Compact light sensor

ABSTRACT

Provided are methods and systems for concurrent imaging at multiple wavelengths. In one aspect, a hyperspectral/multispectral imaging device includes a lens configured to receive light backscattered by an object, a plurality of photo-sensors, a plurality of bandpass filters covering respective photo-sensors, where each bandpass filter is configured to allow a different respective spectral band to pass through the filter, and a plurality of beam splitters in optical communication with the lens and the photo-sensors, where each beam splitter splits the light received by the lens into a plurality of optical paths, each path configured to direct light to a corresponding photo-sensor through the bandpass filter corresponding to the respective photo-sensor.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/969,039, filed Mar. 21, 2014, and U.S. Provisional PatentApplication No. 62/090,302, filed Dec. 10, 2014, the disclosures ofwhich are hereby incorporated by reference herein in their entiretiesfor all purposes.

TECHNICAL FIELD

The present disclosure generally relates to spectroscopy, such ashyperspectral spectroscopy, and in particular, to systems, methods anddevices enabling a compact imaging device.

BACKGROUND

Hyperspectral (also known as “multispectral”) spectroscopy is an imagingtechnique that integrates multiple images of an object resolved atdifferent spectral bands (e.g., ranges of wavelengths) into a singledata structure, referred to as a three-dimensional hyperspectral datacube. Data provided by hyperspectral spectroscopy is often used toidentify a number of individual components of a complex compositionthrough the recognition of spectral signatures of the individualcomponents of a particular hyperspectral data cube.

Hyperspectral spectroscopy has been used in a variety of applications,ranging from geological and agricultural surveying to surveillance andindustrial evaluation. Hyperspectral spectroscopy has also been used inmedical applications to facilitate complex diagnosis and predicttreatment outcomes. For example, medical hyperspectral imaging has beenused to accurately predict viability and survival of tissue deprived ofadequate perfusion, and to differentiate diseased (e.g., cancerous orulcerative) and ischemic tissue from normal tissue.

However, despite the great potential clinical value of hyperspectralimaging, several drawbacks have limited the use of hyperspectral imagingin the clinic setting. In particular, medical hyperspectral instrumentsare costly because of the complex optics and computational requirementsconventionally used to resolve images at a plurality of spectral bandsto generate a suitable hyperspectral data cube. Hyperspectral imaginginstruments can also suffer from poor temporal and spatial resolution,as well as low optical throughput, due to the complex optics and taxingcomputational requirements needed for assembling, processing, andanalyzing data into a hyperspectral data cube suitable for medical use.

Thus, there is an unmet need in the field for less expensive and morerapid means of hyperspectral/multispectral imaging and data analysis.The present disclosure meets these and other needs by providing methodsand systems for concurrently capturing images at multiple wavelengths.

SUMMARY

Various implementations of systems, methods, and devices within thescope of the appended claims each have several aspects, no single one ofwhich is solely responsible for the desirable attributes describedherein. Without limiting the scope of the appended claims, someprominent features are described herein. After considering thisdiscussion, and particularly after reading the section entitled“Detailed Description” one will understand how the features of variousimplementations are used to enable a hyperspectral imaging devicecapable of producing a three-dimensional hyperspectral data cube using aplurality of photo-sensor chips (e.g., CDD, CMOS, etc) suitable for usein a number for applications, and in particular, for medical use.

First Aspect.

Various aspects of the present disclosure are directed to an imagingdevice, including a lens disposed along an optical axis and configuredto receive light that has been emitted from a light source andbackscattered by an object, a plurality of photo-sensors, a plurality ofdual bandpass filters, each respective dual bandpass filter covering arespective photo-sensor of the plurality of photo-sensors and configuredto filter light received by the respective photo-sensor, wherein eachrespective dual bandpass filter is be configured to allow a differentrespective spectral band to pass through the respective dual bandpassfilter, and a plurality of beam splitters in optical communication withthe lens and the plurality of photo-sensors. Each respective beamsplitter is configured to split the light received by the lens into atleast two optical paths. A first beam splitter in the plurality of beamsplitters is in direct optical communication with the lens and a secondbeam splitter in the plurality of beam splitters is in indirect opticalcommunication with the lens through the first beam splitter. Theplurality of beam splitters collectively split the light received by thelens into a plurality of optical paths. Each respective optical path inthe plurality of optical paths is configured to direct light to acorresponding photo-sensor in the plurality of photo-sensors through thedual bandpass filter corresponding to the respective photo-sensor.

In some embodiments, the imaging device further includes at least onelight source having at least a first operating mode and a secondoperating mode. In the first operating mode, the at least one lightsource emits light substantially within a first spectral range, and inthe second operating mode, the at least one light source emits lightsubstantially within a second spectral range.

In some embodiments, each of the plurality of bandpass filters isconfigured to allow light corresponding to either of two discretespectral bands to pass through the filter. In some embodiments, a firstof the two discrete spectral bands corresponds to a first spectral bandthat is represented in the first spectral range and not in the secondspectral range, and a second of the two discrete spectral bandscorresponds to a second spectral band that is represented in the secondspectral range and not in the first spectral range.

In some embodiments, the first spectral range is substantiallynon-overlapping with the second spectral range. In some embodiments, thefirst spectral range is substantially contiguous with the secondspectral range.

In some embodiments, the at least two optical paths from a respectivebeam splitter in the plurality of beam splitters are substantiallycoplanar.

In some embodiments, the imaging device further includes a plurality ofbeam steering elements, each respective beam steering element configuredto direct light in a respective optical path to a respectivephoto-sensor corresponding to the respective optical path. In someembodiments, at least one of the plurality of beam steering elements isconfigured to direct light perpendicular to the optical axis of thelens. In some embodiments, each one of a first subset of the respectivebeam steering elements is configured to direct light in a firstdirection that is perpendicular to the optical axis of the lens, andeach one of a second subset of the respective beam steering elements isconfigured to direct light in a second direction that is perpendicularto the optical axis of the lens and opposite to the first direction.

In some embodiments, a sensing plane of each of the plurality ofphoto-sensors is substantially perpendicular to the optical axis of thelens.

In some embodiments, the imaging device further includes a polarizer inoptical communication with the at least one light source, and apolarization rotator. The polarizer is configured to receive light fromthe at least one light source and project a first portion of the lightfrom the at least one light source onto the object. The first portion ofthe light is polarized in a first manner. The polarizer is furtherconfigured to project a second portion of the light from the at leastone light source onto the polarization rotator. The second portion ofthe light is polarized in a second manner, other than the first manner.In some embodiments, the polarization rotator is configured to rotatethe polarization of the second portion of the light from the secondmanner to the first manner, and project the second portion of the light,polarized in the first manner, onto the object. In some embodiments, thefirst manner is p-polarization and the second manner is s-polarization.In some embodiments, the first manner is s-polarization and the secondmanner is p-polarization.

In some embodiments, the imaging device further includes a controllerconfigured to capture a plurality of images from the plurality ofphoto-sensors by performing a method including using the at least onelight source to illuminate the object with light falling within thefirst spectral range and capturing a first set of images with theplurality of photo-sensors. In such embodiments, the first set of imagesincludes, for each respective photo-sensor, an image corresponding to afirst spectral band transmitted by the corresponding dual bandpassfilter, where the light falling within the first spectral range includeslight falling within the first spectral band of each dual bandpassfilter. The method further comprises using the at least one light sourceto illuminate the object with light falling within the second spectralrange, and capturing a second set of images with the plurality ofphoto-sensors. In such embodiments, the second set of images includes,for each respective photo-sensor, an image corresponding to a secondspectral band transmitted by the corresponding dual bandpass filter,where the light falling within the second spectral range includes lightfalling within the second spectral band of each dual bandpass filter.

In some embodiments, the lens has a fixed focus distance, and theimaging device further includes a first projector configured to projecta first portion of a shape onto the object, and a second projectorconfigured to project a second portion of the shape onto the object,where the first portion of the shape and the second portion of the shapeare configured to converge to form the shape when the lens is positionedat a predetermined distance from the object. This predetermined distancecorresponds to the focal distance of the lens. In some embodiments, theshape indicates a portion of the object that will be imaged by theplurality of photo-sensors when an image is captured with the imagingdevice. In some embodiments, the shape is selected from the groupconsisting of: a rectangle; a square; a circle; and an oval. In someembodiments, the shape is any two-dimensional closed form shape. In someembodiments, the first portion of the shape is a first pair of linesforming a right angle, and the second portion of the shape is a secondpair of lines forming a right angle, where the first portion of theshape and the second portion of the shape are configured to form arectangle on the object when the imaging device is positioned at apredetermined distance from the object.

In some embodiments, each of the plurality of beam splitters exhibits aratio of light transmission to light reflection of about 50:50.

In some embodiments, at least one of the beam splitters in the pluralityof beam splitters is a dichroic beam splitter.

In some embodiments, at least the first beam splitter is a dichroic beamsplitter.

In some embodiments, in the first operating mode, the at least one lightsource emits light substantially within a first spectral range thatincludes at least two discontinuous spectral sub-ranges, and in thesecond operating mode, the at least one light source emits lightsubstantially within a second spectral range.

In some embodiments, the first beam splitter is configured to transmitlight falling within a third spectral range and reflect light fallingwithin a fourth spectral range.

In some embodiments, the plurality of beam splitters includes the firstbeam splitter, the second beam splitter, and a third beam splitter. Insome embodiments, the light falling within the third spectral range istransmitted toward the second beam splitter, and the light fallingwithin the fourth spectral range is reflected toward the third beamsplitter.

In some embodiments, the second and the third beam splitters arewavelength-independent beam splitters.

In some embodiments, the at least two discontinuous spectral sub-rangesof the first spectral range include a first spectral sub-range of about450-550 nm, a second spectral sub-range of about 615-650 nm, and thesecond spectral range is about 550-615 nm.

In some embodiments, the third spectral range is about 585-650 nm, andthe fourth spectral range is about 450-585 nm.

In some embodiments, the third spectral range includes light fallingwithin both the first and the second spectral ranges, and the fourthspectral range includes light falling within both the first and thesecond spectral ranges.

In some embodiments, the first beam splitter is a plate dichroic beamsplitter or a block dichroic beam splitter.

In some embodiments, the first beam splitter, the second beam splitter,and the third beam splitter are dichroic beam splitters.

In some embodiments, in the first operating mode, the at least one lightsource emits light substantially within a first spectral range thatincludes at least two discontinuous spectral sub-ranges, and in thesecond operating mode, the at least one light source emit lightssubstantially within a second spectral range.

In some embodiments, the first beam splitter is configured to transmitlight falling within a third spectral range that includes at least twodiscontinuous spectral sub-ranges and reflect light falling within afourth spectral range that includes at least two discontinuous spectralsub-ranges.

In some embodiments, the plurality of beam splitters includes the firstbeam splitter, the second beam splitter, and a third beam splitter.

In some embodiments, the light falling within the third spectral rangeis transmitted toward the second beam splitter, and the light fallingwithin the fourth spectral range is reflected toward the third beamsplitter.

In some embodiments, the second beam splitter is configured to reflectlight falling within a fifth spectral range that includes at least twodiscontinuous spectral sub-ranges and transmit light not falling withineither of the at least two discontinuous spectral sub-ranges of thefifth spectral sub-range.

In some embodiments, the third beam splitter is configured to reflectlight falling within a sixth spectral range that includes at least twodiscontinuous spectral sub-ranges and transmit light not falling withineither of the at least two discontinuous spectral sub-ranges of thesixth spectral sub-range.

In some embodiments, the at least two discontinuous spectral sub-rangesof the first spectral range include a first spectral sub-range of about450-530 nm, and a second spectral sub-range of about 600-650 nm, and thesecond spectral range is about 530-600 nm.

In some embodiments, the at least two discontinuous spectral sub-rangesof the third spectral range include a third spectral sub-range of about570-600 nm, and a fourth spectral sub-range of about 615-650 nm, and theat least two discontinuous spectral sub-ranges of the fourth spectralrange include a fifth spectral sub-range of about 450-570 nm, and asixth spectral sub-range of about 600-615 nm.

In some embodiments, the at least two discontinuous spectral sub-rangesof the fifth spectral range include a seventh spectral sub-range ofabout 585-595 nm, and an eighth spectral sub-range of about 615-625 nm.

In some embodiments, the at least two discontinuous spectral sub-rangesof the sixth spectral range include a ninth spectral sub-range of about515-525 nm, and a tenth spectral sub-range of about 555-565 nm.

In some embodiments, the first beam splitter, the second beam splitter,and the third beam splitter are each either a plate dichroic beamsplitter or a block dichroic beam splitter.

In some embodiments, the at least one light source includes a first setof light emitting diodes (LEDs) and a second set of LEDs, each LED ofthe first set of LEDs transmits light through a first bandpass filterconfigured to block light falling outside the first spectral range andtransmit light falling within the first spectral range, and each LED ofthe second set of LEDs transmits light through a second bandpass filterconfigured to block light falling outside the second spectral range andtransmit light falling within the second spectral range.

In some embodiments, the first set of LEDs are in a first lightingassembly and the second LEDs are in a second lighting assembly separatefrom the first lighting assembly.

In some embodiments, the first set of LEDs and the second set of LEDsare in a common lighting assembly.

Second Aspect.

Other aspects of the present disclosure are directed to an opticalassembly for an imaging device (e.g, a hyper-spectral/multispectral),including a lens disposed along an optical axis, an optical pathassembly configured to receive light from the lens, a first circuitboard positioned on a first side of the optical path assembly, and asecond circuit board positioned on a second side of the optical pathassembly opposite to the first side. The second circuit board issubstantially parallel with the first circuit board. The optical pathassembly includes a first beam splitter configured to split lightreceived from the lens into a first optical path and a second opticalpath. The first optical path is substantially collinear with the opticalaxis. The second optical path is substantially perpendicular to theoptical axis. A second beam splitter is adjacent to the first beamsplitter. The second beam splitter is configured to split light from thefirst optical path into a third optical path and a fourth optical path.The third optical path is substantially collinear with the first opticalpath, and the fourth optical path is substantially perpendicular to theoptical axis. A third beam splitter is adjacent to the first beamsplitter. The third beam splitter is configured to split light from thesecond optical path into a fifth optical path and a sixth optical path.The fifth optical path is substantially collinear with the secondoptical path, and the sixth optical path is substantially perpendicularto the second optical path. A first beam steering element is adjacent tothe second beam splitter and is configured to deflect light from thethird optical path perpendicular to the third optical path and onto afirst photo-sensor coupled to the first circuit board. A second beamsteering element is adjacent to the second beam splitter and isconfigured to deflect light from the fourth optical path perpendicularto the fourth optical path and onto a second photo-sensor coupled to thesecond circuit board. A third beam steering element is adjacent to thethird beam splitter and is configured to deflect light from the fifthoptical path perpendicular to the fifth optical path and onto a thirdphoto-sensor coupled to the first circuit board. A fourth beam steeringelement is adjacent to the third beam splitter and is configured todeflect light from the sixth optical path perpendicular to the sixthoptical path and onto a fourth photo-sensor coupled to the secondcircuit board.

In some embodiments, the optical assembly further includes a pluralityof bandpass filters. The plurality of bandpass filters includes a firstbandpass filter positioned in the third optical path between the secondbeam splitter and the first photo-sensor, a second bandpass filterpositioned in the fourth optical path between the second beam splitterand the second photo-sensor, a third bandpass filter positioned in thefifth optical path between the third beam splitter and the thirdphoto-sensor, and a fourth bandpass filter positioned in the sixthoptical path between the third beam splitter and the fourthphoto-sensor. Each respective bandpass filter is configured to allow adifferent corresponding spectral band to pass through the respectivebandpass filter.

In some embodiments, at least one respective bandpass filter in theplurality of bandpass filters is a dual bandpass filter.

In some embodiments, the optical assembly further includes a polarizingfilter disposed along the optical axis. In some embodiments, thepolarizing filter is adjacent to the lens and before the first beamsplitter along the optical axis.

In some embodiments, each respective beam steering element is a mirroror prism. In some embodiments, each respective beam steering element isa folding prism.

In some embodiments, each respective beam splitter and each respectivebeam steering element is oriented along substantially the same plane.

In some embodiments, each respective photo-sensor is flexibly coupled toits corresponding circuit board.

In some embodiments, the first beam splitter, the second beam splitter,and the third beam splitter each exhibit a ratio of light transmissionto light reflection of about 50:50.

In some embodiments, at least the first beam splitter is a dichroic beamsplitter.

In some embodiments, the first beam splitter is configured to transmitlight falling within a first spectral range and reflect light fallingwithin a second spectral range.

In some embodiments, the light falling within the first spectral rangeis transmitted toward the second beam splitter, and the light fallingwithin the second spectral range is reflected toward the third beamsplitter.

In some embodiments, the second and the third beam splitters arewavelength-independent beam splitters.

In some embodiments, the first beam splitter, the second beam splitter,and the third beam splitter are dichroic beam splitters.

In some embodiments, the first beam splitter is configured to transmitlight falling within a first spectral range that includes at least twodiscontinuous spectral sub-ranges and reflect light falling within asecond spectral range that includes at least two discontinuous spectralsub-ranges.

In some embodiments, the second beam splitter is configured to reflectlight falling within a third spectral range that includes at least twodiscontinuous spectral sub-ranges and transmit light not falling withineither of the at least two discontinuous spectral sub-ranges of thethird spectral sub-range.

In some embodiments, the third beam splitter is configured to reflectlight falling within a fourth spectral range that includes at least twodiscontinuous spectral sub-ranges and transmit light not falling withineither of the at least two discontinuous spectral sub-ranges of thefourth spectral sub-range.

Third Aspect.

Other aspects of the present disclosure are directed to a lightingassembly for an imaging (e.g., hyper-spectral/multispectral imaging)device, including at least one light source, a polarizer in opticalcommunication with the at least one light source, and a polarizationrotator. The polarizer is configured to receive light from the at leastone light source and project a first portion of the light from the atleast one light source onto an object, where the first portion of thelight exhibits a first type of polarization, and project a secondportion of the light from the at least one light source onto thepolarization rotator, where the second portion of the light exhibits asecond type of polarization. The polarization rotator is configured torotate the polarization of the second portion of the light from thesecond type of polarization to the first type of polarization, andproject the light of the first type of polarization onto the object.

In some embodiments, the first type of polarization is p-polarizationand the second type of polarization is s-polarization. In someembodiments, the first type of polarization is s-polarization and thesecond type of polarization is p-polarization.

In some embodiments, the at least one light source is one or more lightemitting diodes (LED).

In some embodiments, the at least one light source has two or moreoperating modes, each respective operating mode in the two or moreoperation modes including emission of a discrete spectral range oflight, where none of the respective spectral ranges of lightcorresponding to an operating mode completely overlaps with any otherrespective spectral range of light corresponding to a differentoperating mode.

In some embodiments, at least 95% of all of the light received by thepolarizer from the at least one light source is illuminated onto theobject.

Fourth Aspect.

Another aspect of the present disclosure is directed to a method forcapturing an image (e.g., a hyper-spectral/multispectral image) of anobject, including at an imaging system including at least one lightsource, a lens configured to receive light that has been emitted fromthe at least one light source and backscattered by an object, aplurality of photo-sensors, and a plurality of bandpass filters. Eachrespective bandpass filter covers a respective photo-sensor of theplurality of photo-sensors and configured to filter light received bythe respective photo-sensor. Each respective bandpass filter isconfigured to allow a different respective spectral band to pass throughthe respective bandpass filter, illuminating the object with the atleast one light source according to a first mode of operation of the atleast one light source, capturing a first plurality of images, each ofthe first plurality of images being captured by a respective one of theplurality of photo-sensors, wherein each respective image of the firstplurality of images includes light having a different respectivespectral band.

Each of the plurality of bandpass filters is configured to allow lightcorresponding to either of two discrete spectral bands to pass throughthe filter. The method further includes, after capturing the firstplurality of images, illuminating the object with the at least one lightsource according to a second mode of operation of the at least one lightsource, capturing a second plurality of images, each of the secondplurality of images being captured by a respective one of the pluralityof photo-sensors, wherein each respective image of the second pluralityof images includes light having a different respective spectral band,and the spectral bands captured by the second plurality of imagesdifferent than the spectral bands captured by the first plurality ofimages.

In some embodiments, the at least one light source includes a pluralityof light emitting diodes (LEDs).

In some embodiments, a first wavelength optical filter is disposed alongan illumination optical path between a first subset of LEDs in theplurality of LEDs and the object, and a second wavelength optical filteris disposed along an illumination optical path between a second subsetof LEDs in the plurality of LEDs and the object. The first wavelengthoptical filter and the second wavelength optical filter are configuredto allow light corresponding to different spectral bands to pass throughthe respective filters.

In some embodiments, the plurality of LEDs include white light-emittingLEDs. In some embodiments, the plurality of LEDs include a first subsetof LEDs configured to emit light corresponding to a first spectral bandof light and a second subset of LEDs configured to emit lightcorresponding to a second spectral band of light illuminating the objectwith the at least one light source according to a first mode ofoperation consists of illuminating the object with light emitted fromthe first subset of LEDs, and illuminating the object with the at leastone light source according to a second mode of operation consists ofilluminating the object with light emitted from the second subset ofLEDs, where the wavelengths of the first spectral band of light and thewavelengths of the second spectral band of light do not completelyoverlap or do not overlap at all.

Fifth Aspect.

Another aspect of the present disclosure is directed to an imagingdevice (e.g., hyper-spectral/multispectral imaging device), including atleast one light source having at least two operating modes, a lensdisposed along an optical axis and configured to receive light that hasbeen emitted from the at least one light source and backscattered by anobject, a plurality of photo-sensors, a plurality of bandpass filters,each respective bandpass filter covering a respective photo-sensor ofthe plurality of photo-sensors and configured to filter light receivedby the respective photo-sensor. Each respective bandpass filter isconfigured to allow a different respective spectral band to pass throughthe respective bandpass filter. The device further includes one or morebeam splitters in optical communication with the lens and the pluralityof photo-sensors. Each respective beam splitter is configured to splitthe light received by the lens into a plurality of optical paths. Eachoptical path is configured to direct light to a respective photo-sensorthrough the bandpass filter corresponding to the respectivephoto-sensor.

Sixth Aspect.

Another aspect of the present disclosure is directed to an imagingdevice, including a lens disposed along an optical axis and configuredto receive light, a plurality of photo-sensors, an optical path assemblyincluding a plurality of beam splitters in optical communication withthe lens and the plurality of photo-sensors, and a plurality ofmulti-bandpass filters (e.g., dual bandpass filters, triple bandpassfilters, quad-bandpass filters). Each respective multi-bandpass filterin the plurality of multi-bandpass filters covers a correspondingphoto-sensor in the plurality of photo-sensors thereby selectivelyallowing a different corresponding spectral band of light, from thelight received by the lens and split by the plurality of beam splitters,to pass through to the corresponding photo-sensor. Each beam splitter inthe plurality of beam splitters is configured to split the lightreceived by the lens into at least two optical paths. A first beamsplitter in the plurality of beam splitters is in direct opticalcommunication with the lens. A second beam splitter in the plurality ofbeam splitters is in indirect optical communication with the lensthrough the first beam splitter. The plurality of beam splitterscollectively split light received by the lens into a plurality ofoptical paths, wherein each respective optical path in the plurality ofoptical paths is configured to direct light to a correspondingphoto-sensor in the plurality of photo-sensors through themulti-bandpass filter corresponding to the respective photo-sensor.

In a specific embodiment, the multi-bandpass filters are dual bandpassfilters. In some implementations, each respective optical detector inthe plurality of optical detectors (e.g., optical detectors 112) iscovered by a dual-band pass filter (e.g., filters 114).

In some implementations, each respective optical detector is covered bya triple band pass filter, enabling use of a third light source andcollection of three sets of images at unique spectral bands. Forexample, four optical detectors can collect images at up to twelveunique spectral bands, when each detector is covered by a tripleband-pass filter.

In some implementations, each respective optical detector is covered bya quad-band pass filter, enabling use of a fourth light source andcollection of four sets of images at unique spectral bands. For example,four optical detectors can collect images at up to sixteen uniquespectral bands, when each detector is covered by a quad band-passfilter. In yet other implementations, band pass filters allowing passageof five, six, seven, or more bands each can be used to collect largersets of unique spectral bands.

In some embodiments, the imaging device also includes a first lightsource and a second light source, wherein the first light source and thesecond light source are configured to shine light so that a portion ofthe light is backscattered by the object and received by the lens.

In some embodiments, the first light source emits light that issubstantially limited to a first spectral range, and the second lightsource emits light that is substantially limited to a second spectralrange.

In some embodiments, the first light source is a first multi-spectrallight source covered by a first bandpass filter, wherein the firstbandpass filter substantially blocks all light emitted by the firstlight source other than the first spectral range, and the second lightsource is a second multi-spectral light source covered by a secondbandpass filter, wherein the second bandpass filter substantially blocksall light emitted by the second light source other than the secondspectral range.

In some embodiments, the first multi-spectral light source is a firstwhite light emitting diode and the second multi-spectral light source isa second white light emitting diode.

In some embodiments, each respective dual bandpass filter in theplurality of dual bandpass filters is configured to selectively allowlight corresponding to either of two discrete spectral bands to passthrough to the corresponding photo-sensor. In some embodiments, a firstof the two discrete spectral bands corresponds to a first spectral bandthat is represented in the first spectral range and not in the secondspectral range, and a second of the two discrete spectral bandscorresponds to a second spectral band that is represented in the secondspectral range and not in the first spectral range.

In some embodiments, the first spectral range is substantiallynon-overlapping with the second spectral range.

In some embodiments, the first spectral range is substantiallycontiguous with the second spectral range.

In some embodiments, the first spectral range comprises wavelengths 520nm, 540 nm, 560 nm and 640 nm wavelength light, and the second spectralrange comprises of 580 nm, 590 nm, 610 nm and 620 nm wavelength light.

In some embodiments, the at least two optical paths from a respectivebeam splitter in the plurality of beam splitters are substantiallycoplanar.

In some embodiments, the imaging device further includes a plurality ofbeam steering elements, each respective beam steering element configuredto direct light in a respective optical path to a respectivephoto-sensor, of the plurality of photo-sensors, corresponding to therespective optical path. In some embodiments, at least one of theplurality of beam steering elements is configured to direct lightperpendicular to the optical axis of the lens. In some embodiments, eachone of a first subset of the plurality of beam steering elements isconfigured to direct light in a first direction that is perpendicular tothe optical axis, and each one of a second subset of the plurality ofbeam steering elements is configured to direct light in a seconddirection that is perpendicular to the optical axis and opposite to thefirst direction.

In some embodiments, a sensing plane of each of the plurality ofphoto-sensors is substantially perpendicular to the optical axis.

In some embodiments, the imaging device further includes a controllerconfigured to capture a plurality of images from the plurality ofphoto-sensors by performing a method that includes illuminating theobject a first time using the first light source, and capturing a firstset of images with the plurality of photo-sensors during theillumination. The first set of images includes, for each respectivephoto-sensor in the plurality of photo-sensors, an image correspondingto a first spectral band transmitted by the corresponding multi-bandpassfilter (e.g., dual bandpass filter), where the light falling within thefirst spectral range includes light falling within the first spectralband of each multi-bandpass filter (e.g., dual bandpass filter). Themethod further includes extinguishing the first light source, and thenilluminating the object a second time using the second light source. Themethod including capturing a second set of images with the plurality ofphoto-sensors during the second illumination. The second set of imagesincludes, for each respective photo-sensor in the plurality ofphoto-sensors, an image corresponding to a second spectral bandtransmitted by the corresponding multi-bandpass filter (e.g., dualbandpass filter), where the light falling within the second spectralrange includes light falling within the second spectral band of eachmulti-bandpass filter (e.g., dual bandpass filter).

In some embodiments, each respective photo-sensor in the plurality ofphoto-sensors is a pixel array that is controlled by a correspondingshutter mechanism that determines an image integration time for therespective photo-sensor. A first photo-sensor in the plurality ofphoto-sensors is independently associated with a first integration timefor use during the first image capture and a second integration time foruse during the second image capture. The first integration time isindependent of the second integration time. In other words, the devicedetermines separate integration times for each spectral band at which animage is captured.

In some embodiments, each respective photo-sensor in the plurality ofphoto-sensors is a pixel array that is controlled by a correspondingshutter mechanism that determines an image integration time for therespective photo-sensor. A duration of the first illumination isdetermined by a first maximum integration time associated with theplurality of photo-sensors during the first image capture, where anintegration time of a first photo-sensor in the plurality ofphoto-sensors is different than an integration time of a secondphoto-sensor in the plurality of photo-sensors during the first imagecapture. A duration of the second illumination is determined by a secondmaximum integration time associated with the plurality of photo-sensorsduring the second capture, where an integration time of the firstphoto-sensor is different than an integration time of the secondphoto-sensor during the second capture. In some implementations, thefirst maximum integration time is different than the second maximumintegration time.

In some embodiments, each beam splitter in the plurality of beamsplitters exhibits a ratio of light transmission to light reflection ofabout 50:50.

In some embodiments, at least one of the beam splitters in the pluralityof beam splitters is a dichroic beam splitter.

In some embodiments, at least the first beam splitter (e.g., in directoptical communication with the lens) is a dichroic beam splitter.

In some embodiments, at least one of the beam splitters in the pluralityof beam splitters is a dichroic beam splitter, the first spectral rangeincludes at least two discontinuous spectral sub-ranges, each of theplurality of beam splitters exhibits a ratio of light transmission tolight reflection of about 50:50, and the first beam splitter isconfigured to transmit light falling within a third spectral range andreflect light falling within a fourth spectral range.

In some embodiments, the plurality of beam splitters includes the firstbeam splitter, the second beam splitter, and a third beam splitter.

In some embodiments, the light falling within the third spectral rangeis transmitted toward the second beam splitter, and the light fallingwithin the fourth spectral range is reflected toward the third beamsplitter.

In some embodiments, the second and the third beam splitters arewavelength-independent beam splitters.

In some embodiments, the third spectral range includes light fallingwithin both the first and the second spectral ranges, and the fourthspectral range includes light falling within both the first and thesecond spectral ranges.

In some embodiments, the first beam splitter is a plate dichroic beamsplitter or a block dichroic beam splitter. In some embodiments, thefirst beam splitter, the second beam splitter, and the third beamsplitter are dichroic beam splitters.

In some embodiments, the first spectral range includes at least twodiscontinuous spectral sub-ranges, each of the plurality of beamsplitters exhibits a ratio of light transmission to light reflection ofabout 50:50, the first beam splitter is configured to transmit lightfalling within a third spectral range and reflect light falling within afourth spectral range, the plurality of beam splitters includes thefirst beam splitter, the second beam splitter, and a third beamsplitter, and the first beam splitter, the second beam splitter, and thethird beam splitter are dichroic beam splitters.

In some embodiments, the third spectral range includes at least twodiscontinuous spectral sub-ranges, and the fourth spectral rangeincludes at least two discontinuous spectral sub-ranges.

In some embodiments, the light falling within the third spectral rangeis transmitted toward the second beam splitter, and the light fallingwithin the fourth spectral range is reflected toward the third beamsplitter.

In some embodiments, the second beam splitter is configured to reflectlight falling within a fifth spectral range that includes at least twodiscontinuous spectral sub-ranges and transmit light not falling withineither of the at least two discontinuous spectral sub-ranges of thefifth spectral sub-range.

In some embodiments, the third beam splitter is configured to reflectlight falling within a sixth spectral range that includes at least twodiscontinuous spectral sub-ranges and transmit light not falling withineither of the at least two discontinuous spectral sub-ranges of thesixth spectral sub-range.

In some embodiments, the first beam splitter, the second beam splitter,and the third beam splitter are each either a plate dichroic beamsplitter or a block dichroic beam splitter.

In some embodiments, the first light source is in a first lightingassembly and the second light source is in a second lighting assemblyseparate from the first lighting assembly.

In some embodiments, each image in the plurality of images is amulti-pixel image of a location on the object, the method performed bythe controller also includes combining each image in the plurality ofimages, on a pixel by pixel basis, to form a composite image.

In some embodiments (e.g., where tri-bandpass filters or quad-bandpassfilters are employed), the imaging system includes more than two lightsources. In one embodiment, the imaging device includes at least threelight sources. In one embodiment, the imaging includes at least fourlight sources. In one embodiment, the imaging device includes at leastfive light sources.

In some embodiments, the imaging device is portable and poweredindependent of a power grid during the first and second illuminations.The first light source provides at least 80 watts of illuminating powerduring the first illumination. The second light source provides at least80 watts of illuminating power during the second illumination. Theimaging device further includes a capacitor bank in electricalcommunication with the first light source and the second light source,wherein a capacitor in the capacitor bank has a voltage rating of atleast 2 volts and a capacitance rating of at least 80 farads.

In some embodiments, the first and second wavelengths provide anilluminating power, during their respective illuminations, selectedindependently from between 20 watts and 400 watts. In some embodiments,the illuminating powers are independently selected from about 20 watts,30 watts, 40 watts, 50 watts, 60 watts, 70 watts, 80 watts, 90 watts,100 watts, 110 watts, 120 watts, 130 watts, 140 watts, 150 watts, 160watts, 170 watts, 180 watts, 190 watts, 200 watts, 225 watts, 250 watts,275 watts, 300 watts, 325 watts, 350 watts, 375 watts, and 400 watts.

In some embodiments, discrete bands of a multi-bandpass filter are eachseparated by at least 60 nm. In a particular embodiment, the twodiscrete bands of a dual bandpass filter in the plurality of dualbandpass filters are separated by at least 60 nm.

In some embodiments, the imaging device is portable and electricallyindependent of a power grid during the first and second illuminations(or during all illuminations where more than two illuminations areemployed). In some embodiments, the first and second illuminations occurfor less than 300 milliseconds (or all illuminations last for less than300 milliseconds where more than two illuminations are employed).

In some embodiments, the imaging device also includes a first circuitboard positioned on a first side of the optical path assembly, where afirst photo-sensor and a third photo-sensor in the plurality ofphoto-sensors are coupled to the first circuit board. A second circuitboard positioned on a second side of the optical path assembly oppositeto the first side, where the second circuit board is substantiallyparallel with the first circuit board, where a second photo-sensor and afourth photo-sensor in the plurality of photo-sensors are coupled to thesecond circuit board. The first beam splitter is configured to splitlight received from the lens into a first optical path and a secondoptical path, where the first optical path is substantially collinearwith the optical axis, and the second optical path is substantiallyperpendicular to the optical axis. The second beam splitter isconfigured split light from the first optical path into a third opticalpath and a fourth optical path, where the third optical path issubstantially collinear with the first optical path, and the fourthoptical path is substantially perpendicular to the optical axis. A thirdbeam splitter in the plurality of beam splitters is configured to splitlight from the second optical path into a fifth optical path and a sixthoptical path, where the fifth optical path is substantially collinearwith the second optical path, and the sixth optical path issubstantially perpendicular to the second optical path. The optical pathassembly also includes a first beam steering element configured todeflect light from the third optical path perpendicular to the thirdoptical path and onto the first photo-sensor coupled to the firstcircuit board, a second beam steering element configured to deflectlight from the fourth optical path perpendicular to the fourth opticalpath and onto the second photo-sensor coupled to the second circuitboard, a third beam steering element configured to deflect light fromthe fifth optical path perpendicular to the fifth optical path and ontothe third photo-sensor coupled to the first circuit board, and a fourthbeam steering element configured to deflect light from the sixth opticalpath perpendicular to the sixth optical path and onto the fourthphoto-sensor coupled to the second circuit board.

In some embodiments, a first multi-bandpass filter (e.g., dual bandpassfilter) is positioned in the third optical path between the first beamsplitter and the first photo-sensor. A second multi-bandpass filter(e.g., dual bandpass filter) is positioned in the fourth optical pathbetween the second beam splitter and the second photo-sensor. A thirdmulti-bandpass filter (e.g., dual bandpass filter) is positioned in thefifth optical path between the third beam splitter and the thirdphoto-sensor. A fourth multi-bandpass filter (e.g., dual bandpassfilter) is positioned in the sixth optical path between the fourth beamsplitter and the fourth photo-sensor.

In some embodiments, the imaging device also includes a polarizingfilter disposed along the optical axis. In some embodiments, thepolarizing filter is adjacent to the lens and before the first beamsplitter along the optical axis.

In some embodiments, the first beam steering element is a mirror orprism.

In some embodiments, the first beam steering element is a folding prism.

In some embodiments, each respective beam splitter and each respectivebeam steering element is oriented along substantially the same plane.

In some embodiments, each respective photo-sensor is flexibly coupled toits corresponding circuit board.

In some embodiments, the first beam splitter, the second beam splitter,and the third beam splitter each exhibits a ratio of light transmissionto light reflection of about 50:50.

In some embodiments, at least the first beam splitter is a dichroic beamsplitter.

In some embodiments, the first beam splitter is configured to transmitlight falling within a first spectral range and reflect light fallingwithin a second spectral range.

In some embodiments, the light falling within the first spectral rangeis transmitted toward the second beam splitter, and the light fallingwithin the second spectral range is reflected toward the third beamsplitter.

In some embodiments, the second and the third beam splitters arewavelength-independent beam splitters.

In some embodiments, the first beam splitter, the second beam splitter,and the third beam splitter are dichroic beam splitters.

In some embodiments, the first beam splitter is configured to transmitlight falling within a first spectral range that includes at least twodiscontinuous spectral sub-ranges and reflect light falling within asecond spectral range that includes at least two discontinuous spectralsub-ranges.

In some embodiments, the second beam splitter is configured to reflectlight falling within a third spectral range that includes at least twodiscontinuous spectral sub-ranges and transmit light not falling withineither of the at least two discontinuous spectral sub-ranges of thethird spectral sub-range.

In some embodiments, the third beam splitter is configured to reflectlight falling within a fourth spectral range that includes at least twodiscontinuous spectral sub-ranges and transmit light not falling withineither of the at least two discontinuous spectral sub-ranges of thefourth spectral sub-range.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the present disclosure can be understood in greater detail, amore particular description may be had by reference to the features ofvarious implementations, some of which are illustrated in the appendeddrawings. The appended drawings, however, merely illustrate the morepertinent features of the present disclosure and are therefore not to beconsidered limiting, for the description may admit to other effectivefeatures and arrangements.

FIG. 1A is an illustration of a hyperspectral imaging device 100, inaccordance with an implementation.

FIG. 1B is an illustration of a hyperspectral imaging device 100, inaccordance with an implementation.

FIG. 2A and FIG. 2B are illustrations of an optical assembly 102 of ahyperspectral imaging device 100, in accordance with implementations ofthe disclosure.

FIG. 3 is an exploded schematic view of an implementation of an opticalassembly 102 of a hyperspectral imaging device 100.

FIG. 4 is an exploded schematic view of the optical paths 400-404 of animplementation of an optical assembly 102 of a hyperspectral imagingdevice 100.

FIG. 5A, FIG. 5B, and FIG. 5C are two-dimensional schematicillustrations of the optical paths 500-506 and 600-606 ofimplementations of an optical assembly 102 of a hyperspectral imagingdevice 100.

FIG. 6 is an illustration of a front view of implementations of anoptical assembly 102 of a hyperspectral imaging device 100.

FIG. 7 is a partially cut-out illustration of a bottom view of ahyperspectral imaging device 100, in accordance with an implementation.

FIG. 8A is a partially cut-out illustration of a bottom view of ahyperspectral imaging device 100 and optical paths, in accordance withan implementation.

FIG. 8B is a partially cut-out illustration of a bottom view of ahyperspectral imaging device 100 and optical paths, in accordance withanother implementation.

FIG. 9A, FIG. 9B and FIG. 9C are illustrations of framing guides 902projected onto the surface of an object for focusing an image collectedby implementations of a hyperspectral imaging device 100.

FIGS. 9D and 9E are illustrations of point guides 903 projected onto thesurface of an object for focusing an image collected by implementationsof a hyperspectral imaging device 100.

FIG. 10 is a two-dimensional schematic illustration of the optical pathsof an implementation of an optical assembly 102 of a hyperspectralimaging device 100.

FIG. 11 is a two-dimensional schematic illustration of the optical pathsof another implementation of an optical assembly 102 of a hyperspectralimaging device 100.

FIG. 12 is a two-dimensional schematic illustration of the optical pathsof an implementation of an optical assembly 102 of a hyperspectralimaging device 100.

FIG. 13 is an illustration of a first view of another hyperspectralimaging device 100, in accordance with an implementation.

FIG. 14 is an illustration of a second view of the hyperspectral imagingdevice 100 of FIG. 13, in accordance with an implementation.

In accordance with common practice the various features illustrated inthe drawings may not be drawn to scale. Accordingly, the dimensions ofthe various features may be arbitrarily expanded or reduced for clarity.In addition, some of the drawings may not depict all of the componentsof a given system, method or device. Finally, like reference numeralsmay be used to denote like features throughout the specification andfigures.

DETAILED DESCRIPTION

Numerous details are described herein in order to provide a thoroughunderstanding of the example implementations illustrated in theaccompanying drawings. However, the invention may be practiced withoutmany of the specific details. And, well-known methods, components, andcircuits have not been described in exhaustive detail so as not tounnecessarily obscure more pertinent aspects of the implementationsdescribed herein.

Hyperspectral imaging typically relates to the acquisition of aplurality of images, where each image represents a narrow spectral bandcollected over a continuous spectral range. For example, a hyperspectralimaging system may acquire 15 images, where each image represents lightwithin a different spectral band. Acquiring these images typicallyentails taking a sequence of photographs of the desired object, andsubsequently processing the multiple images to generate the desiredhyperspectral image. In order for the images to be useful, however, theymust be substantially similar in composition and orientation. Forexample, the subject of the images must be positioned substantiallyidentically in each frame in order for the images to be combinable intoa useful hyperspectral image. Because images are captured sequentially(e.g., one after another), it can be very difficult to ensure that allof the images are properly aligned. This can be especially difficult inthe medical context, where a clinician is capturing images of a patientwho may move, or who may be positioned in a way that makes imaging thesubject area difficult or cumbersome.

As described herein, a hyperspectral imaging device is described thatconcurrently captures multiple images, where each image is captured in adesired spectral band. Specifically, the disclosed imaging device andassociated methods use multiple photo-sensors to capture a plurality ofimages concurrently. Thus, a user does not need to maintain perfectalignment between the imaging device and a subject while attempting tocapture multiple discrete images, and can instead simply position theimaging device once and capture all of the required images in a singleoperation (e.g., with, one, two, or three exposures) of the imagingdevice. Accordingly, hyperspectral images can be acquired faster andmore simply, and with more accurate results.

Conventional imaging systems also suffer from high power budget demands,requiring the system to be plugged into a power source (e.g., analternating current outlet) for operation. This arises from the use oftunable filter elements, high powered light sources, etc.Advantageously, the optical architecture of the hyperspectral imagingdevices described herein reduces the power burden and overall size ofthe system, allowing production of a truly portable device.

In one implementation, the design of the hyperspectral imaging devicesdescribed herein solve these problems by employing a plurality ofphoto-sensors configured to concurrently acquire images of an object(e.g., a tissue of a patient) at different spectral bands. Eachphoto-sensor is configured to detect a limited number of spectral bands(e.g., 1 or 2 spectral bands), but collectively, the plurality ofphoto-sensors capture images at all of the spectral bands required toconstruct a particular hyperspectral data cube (e.g., a hyperspectraldata cube useful for generating a particular medical diagnosis,performing surveillance, agricultural surveying, industrial evaluation,etc.).

In some implementations, these advantages are realized by separating anddirecting light within an optical assembly in the imaging device suchthat each photo-sensor is irradiated with light of only limited spectralbands. An example of the optical paths created within the opticalassembly of such an implementation is illustrated in FIG. 11, whichsplits light into component spectral bands (e.g., using dichroic beamsplitters and/or beam splitting plates) and direct appropriate spectralbands of light to corresponding photo-sensors.

In some implementations, these advantages are realized by evenlydistributing light towards each photo-sensor within an optical assembly,and then filtering out unwanted wavelengths prior to detection by eachphoto-sensor. An example of the optical paths created within the opticalassembly of such an implementation is illustrated in FIG. 10, which usesoptical elements (e.g., 50:50 beam splitters) to evenly distribute lighttowards filter elements covering each respective photo-sensor.

In yet other implementations, these advantages are realized by employinga hybrid of these two strategies. For example, with an optical assemblythat first separates light (e.g., with a dichroic beam splitter or beamsplitting plate) and then evenly distributes component spectral bands torespective photo-sensors covered by filters having desired passbandspectrums.

In some implementations, one or more of these advantages are realized byemploying two illumination sources in the hyperspectral imaging device.The first illumination source is configured to illuminate an object witha first sub-set of spectral bands, and the second illuminationconfigured to illuminate the object with a second sub-set of spectralbands. The first and second subsets of spectral bands do not overlap,but together include all the spectral bands required to construct aparticular hyperspectral data cube. The optical assembly is configuredsuch that two sets of images are collected, the first while the objectis illuminated with the first light source and the second while theobject is illuminated with the second light source. For example, eachphoto-sensor captures a first image at a first spectral band included inthe first sub-set of spectral bands and a second image at a secondspectral band included in the second sub-set of spectral bands.

In some implementations, image capture and processing includes theimaging device collecting a plurality of images of a region of intereston a subject (e.g., a first image captured at a first spectral bandwidthand a second image captured at a second spectral bandwidth). The imagingdevice stores each respective image at a respective memory location(e.g., the first image is stored at a first location in memory and thesecond image is stored at a second location in memory). And the imagingdevice compares, on a pixel-by-pixel basis, e.g., with a processor 210,each pixel of the respective images to produce a hyperspectral image ofthe region of interest of the subject. In some implementations,individual pixel values are binned, averaged, or otherwisearithmetically manipulated prior to pixel-by-pixel analysis, e.g.,pixel-by-pixel comparison includes comparison of binned, averaged, orotherwise arithmetically manipulated pixel values.

Exemplary Implementations

FIG. 1A illustrates a hyperspectral imaging device 100, in accordancewith various implementations. The hyperspectral imaging device 100includes an optical assembly 102 having at least one light source 106for illuminating the surface of an object (e.g., the skin of a subject)and a lens assembly 104 for collecting light reflected and/or backscattered from the object. The optical assembly 102 is mounted onto adocking station 110.

In various implementations, optical assembly 102 is permanently fixedonto the docking station 110 (e.g., optical assembly 102 is held inplace by a substructure of docking station 110 partially encasingoptical assembly 102 and fastened through welding, screws, or othermeans). In other implementations, optical assembly 102 is notpermanently fixed onto the docking station 110 (e.g., optical assembly102 snaps into a substructure of docking station 110).

In various optional implementations, and with reference to FIG. 1A,docking station 110 includes first and second projectors 112-1 and 112-2configured to project light onto the object indicating when thehyperspectral imaging device 100 is positioned at an appropriatedistance from the object to acquire a focused image. This may beparticularly useful where the lens assembly 104 has a fixed focaldistance, such that the image cannot be brought into focus bymanipulation of the lens assembly.

Referring additionally to FIGS. 8A and 9C, in various implementations,first projector 112-1 and second projector 112-2 of FIG. 1A areconfigured to project patterns of light onto the to-be-imaged objectincluding a first portion 902-1 and a second portion 902-2 that togetherform a shape 902 on the object when properly positioned (see, e.g.,FIGS. 8A and 9C). For example, the first portion of the shape 902-1 andthe second portion of the shape 902-1 are configured to converge to formthe shape 902 when the lens 104 is positioned at a predetermineddistance from the object, the predetermined distance corresponding to afocal distance of the lens assembly 104.

In various implementations, first projector 112-1 and second projector112-2 are each configured to project a spot onto the object, such thatthe spots converge when the lens 104 is positioned at a predetermineddistance from the object corresponding to a focus distance of the lens(see, e.g., FIGS. 8B and 9E). Other projections are also contemplated,including other shapes, reticles, images, crosshairs, etc.

In various implementations, docking station 110 includes an opticalwindow 114 configured to be positioned between light source 106 and anobject to be imaged. Window 114 is also configured to be positionedbetween lens assembly 104 and the object to be imaged. Optical window114 protects light source 106 and lens assembly 104, as well as limitsambient light from reaching lens assembly 104. In variousimplementations, optical window 114 consists of a material that isoptically transparent (or essentially optically transparent) to thewavelengths of light emitted by light source 106. In variousimplementations, optical window 114 consists of a material that ispartially or completely opaque to one or more wavelengths of light notemitted by light source 106. In various implementations, optical window114 serves as a polarizing lens. In various implementations, opticalwindow 114 is open to the external environment (e.g., does not includean installed lens or other optically transparent material).

In various implementations, docking station 110 is configured to receivea mobile device 120, such as a smart phone, a personal digital assistant(PDA), an enterprise digital assistant, a tablet computer, an IPOD, adigital camera, a portable music player, and/or other portableelectronic devices, effectively mounting the mobile device ontohyperspectral imaging device 100. In various implementations, dockingstation 110 is configured to facilitate electronic communication betweenoptical assembly 102 and mobile device 120. In various implementations,mobile device 120 includes display 122 configured to act as a displayfor optical assembly 102 (e.g., as a touch screen display for operatingoptical assembly 102 and/or as a display for hyperspectral imagescollected by optical assembly 102). In various implementations, mobiledevice 120 is configured as a processor for processing one or moreimages collected by optical assembly 102. In various implementations,mobile device 120 is configured to transmit one or more images collectedby optical assembly 102 to an external computing device (e.g., by wiredor wireless communication).

FIG. 1B illustrates another hyperspectral imaging device 100, inaccordance with various implementations, similar to that shown in FIG.1A but including an integrated body 101 that resembles a digitalsingle-lens reflex (DSLR) camera in that the body has a forward-facinglens assembly 104, and a rearward facing display 122. The DSLR-typehousing allows a user to easily hold hyperspectral imaging device 100,aim it toward a patient and the region of interest (e.g., the skin ofthe patient), and position the device at an appropriate distance fromthe patient. One will appreciate that the implementation of FIG. 1B, mayincorporate the various features described above and below in connectionwith the device of FIG. 1A.

In various implementations, and similar to the device described above,the hyperspectral imaging device 100 illustrated in FIG. 1B includes anoptical assembly having light sources 106 and 107 for illuminating thesurface of an object (e.g., the skin of a subject) and a lens assembly104 for collecting light reflected and/or back scattered from theobject.

In various implementations, and also similar to the device describedabove, the hyperspectral imaging device of FIG. 1B includes first andsecond projectors 112-1 and 112-2 configured to project light onto theobject indicating when the hyperspectral imaging device 100 ispositioned at an appropriate distance from the object to acquire afocused image. As noted above, this may be particularly useful where thelens assembly 104 has a fixed focus distance, such that the image cannotbe brought into focus by manipulation of the lens assembly. As shown inFIG. 1B, the projectors are mounted on a forward side of body 101.

In various implementations, the body 101 substantially encases andsupports the light sources 106 and 107 and the lens assembly 104 of theoptical assembly, along with the first and second projectors 112-1 and112-2 and the display 122.

In contrast to the above-described device, various implementations ofthe hyperspectral imaging device of FIG. 1B include photo-sensorsmounted on substantially vertically-oriented circuit boards (see, e.g.,photo sensors 210-1, 210-3). In various implementations, thehyperspectral imaging device includes a live-view camera 103 and aremote thermometer 105. The live-view camera 103 enables the display 122to be used as a viewfinder, in a manner similar to the live previewfunction of DSLRs. The thermometer 105 is configured to measure thetemperature of the patient's tissue surface within the region ofinterest.

FIG. 2A is a cutaway view of the optical assembly 102 for ahyperspectral imaging device 100, in accordance with variousimplementations. The optical assembly 102 may be incorporated into alarger assembly (as discussed herein), or used independently of anyother device or assembly.

As shown in FIG. 2A, the optical assembly 102 includes a casing 202. Asalso shown in an exploded view in FIG. 3, the optical assembly 102 alsoincludes a lens assembly 104, at least one light source (e.g., lightsource 106), an optical path assembly 204, one or more circuit boards(e.g., circuit board 206 and circuit board 208), and a plurality ofphoto-sensors 210 (e.g., photo-sensors 210-1 . . . 210-4). One willappreciate that the imaging device 100 is provided with one or moreprocessors and a memory. For example, such processors may be integratedor operably coupled with the one or more circuit boards. For instance,in some embodiments, an AT32UC3A364 (ATMEL corporation, San Jose Calif.)microcontroller, or equivalent, coupled to one or more floating pointgate arrays, is used to collect images from the photo-sensors. Althoughillustrated with two circuit boards 206 and 208, in someimplementations, the hyperspectral imaging device has a single circuitboard (e.g., either 206 or 208) and each photo-sensor 210 is eithermounted on the single circuit board or connected to the circuit board(e.g., by a flex circuit or wire).

Components of the optical assembly 102 are housed in and/or mounted tothe casing 202. In various implementations, the casing 202 is itselfconfigured to be housed in and/or mounted to another assembly, as shownin FIG. 1A.

The lens assembly 104 (also referred to interchangeably herein as a“lens”) is an imaging lens that is configured to capture light reflectedfrom objects, focus the light, and direct the light into the opticalpath assembly 204. In various implementations, the lens assembly 104 isa multi-element lens having a fixed focal length, a fixed focusdistance, and/or is a fixed-focus lens.

The at least one light source is configured to direct light onto anobject to be imaged by the optical assembly 102. Specifically, the atleast one light source is configured to illuminate an object with lighthaving desired spectral content. Light from the at least one lightsource that is reflected or backscattered from the object is thenreceived by the lens assembly 104 and captured by the plurality ofphoto-sensors in the optical assembly 102.

In various implementations, as discussed herein, the at least one lightsource is configured to operate according to two or more modes ofoperation, where each mode of operation results in the illumination ofthe object with light having different spectral content. For example, ina first mode of operation, the at least one light source emits lightwithin a spectral range of 500 nm to 600 nm (or any other appropriatespectral range), and, in a second mode of operation, the at least onelight source emits light within a spectral range of 600 nm to 700 nm (orany other appropriate spectral range).

In various implementations, the light source includes a single broadbandlight source, a plurality of broadband light sources, a singlenarrowband light source, a plurality of narrowband light sources, or acombination of one or more broadband light source and one or morenarrowband light source. Likewise, in various embodiments, the lightsource includes a plurality of coherent light sources, a singleincoherent light source, a plurality of incoherent light sources, or acombination of one or more coherent and one or more incoherent lightsources.

In one implementation, where a light source is configured to emit lightwithin two or more spectral ranges, the light source includes two ormore sets (e.g., each respective set including one or more light sourcesconfigured to emit light of the same spectral band) of light emittingdevices (e.g., light emitting diodes), where each respective set isconfigured to only emit light within one of the two or more spectralranges.

In some embodiments, referring to FIG. 1B, where a light source isconfigured to emit light within two or more spectral ranges, the lightsource includes two or more sets of light emitting devices (e.g., lightemitting diodes), where each respective set is filtered by a respectivefilter (e.g., a bandpass filter). As a specific example, referring toFIG. 1B, light source 106 is configured to emit light within a firstspectral range and light source 107 is configured to emit light within asecond spectral range. In some embodiments, light source 106 comprises afirst set of light emitting devices that are filtered with a firstbandpass filter corresponding to the first spectral range, and lightsource 107 comprises a second set of light emitting devices filteredwith a second bandpass filters corresponding to the second spectral. Intypical embodiments the first spectral range is different from, andnon-overlapping, the first second spectral range. In some embodimentsthe first spectral range is different from, but overlapping, the secondspectral range. In some embodiments the first spectral range is the sameas the second spectral range. In some embodiments, the first set oflight emitting devices consists of a first single light emitting diode(LED) and the second set of light emitting devices consists of a secondsingle light emitting diode. An example of a suitable light emittingdiode for use as the first single light emitting diode and the secondsingle light emitting diode in such embodiments is a LUMINUS CBT-140Whtie LED (Luminus Devices, Inc., Billerica, Mass.). In someembodiments, the first set of light emitting devices consists of a firstplurality of light emitting diode and the second set of light emittingdevices consists of a second plurality of light emitting diodes.

In some embodiments the light source 106 is not covered by a bandpassfilter and natively emits only the first spectral range. In someembodiments the second source 107 is not covered by a bandpass filterand natively emits only the second spectral range.

In some embodiments, the light source 106 emits at least 80 watts ofilluminating power and the second light source emits at least 80 wattsof illuminating power. In some embodiments, the light sourceindependently 106 emits at least 80 watts, at least 85 watts, at least90 watts, at least 95 watts, at least 100 watts, at least 105 watts, orat least 110 watts of illuminating power. In some embodiments, the lightsource 107 independently emits at least 80 watts, at least 85 watts, atleast 90 watts, at least 95 watts, at least 100 watts, at least 105watts, or at least 110 watts of illuminating power.

In some embodiments, the spectral imager 100 is not connected to a mainpower supply (e.g., an electrical power grid) during illumination. Inother words, in some embodiments, the spectral imager is independentlypowered, e.g. by a battery, during at least the illumination stages. Insome embodiments, in order to achieve the amount of illuminating powerneeded by light source 106 and/or light source 107 (e.g., more than 100watts of illuminating power in some embodiments), the light sources arein electrical communication to the battery through a high performancecapacity bank (not shown). In one such example, the capacitor bankcomprises a board mountable capacitor. In one such example, thecapacitor bank comprises a capacitor having a rating of at least 80farads (F), a peak current of at least 80 amperes (A), and is capable ofdelivering at least 0.7 watt-hours (Whr) of energy during illumination.In one such example, the capacitor bank comprises a capacitor having arating of at least 90 F, a peak current of at least 85 A, and is capableof delivering at least 0.8 Whr of energy during illumination. In onesuch example, the capacitor bank comprises a capacitor having a ratingof at least 95 F, a peak current of at least 90 A, and is capable ofdelivering at least 0.9 Whr of energy during illumination. In one suchexample, the capacitor bank comprises an RSC2R7107SR capacitor (IOXUS,Oneonta, N.Y.), which has a rating of 100 F, a peak current of 95 A, andis capable of delivering 0.1 Whr of energy during illumination.

In one example, the battery used to power the spectral imager, includingthe capacitor bank, has a voltage of at least 6 volts and a capacity ofat least 5000 mAH. In one such example, the battery is manufactured byTENERGY (Fremont, Calif.), is rated for 7.4 V, has a capacitance of 6600mAH, and weighs 10.72 ounces.

In some embodiments, the capacitor bank comprises a single capacitor inelectrical communication with both the light source 106 and the lightsource 107, where the single capacitor has a rating of at least 80 F, apeak current of at least 80 A, and is capable of delivering at least 0.7Whr of energy during illumination. In some embodiments, the capacitorbank comprises a first capacitor in electrical communication with thelight source 106 and a second capacitor in electrical communication withlight source 107, where the first capacitor and the second capacitoreach have a rating of at least 80 F, a peak current of at least 80 A,and are each capable of delivering at least 0.7 Whr of energy duringillumination.

In one implementation, where a light source is configured to emit lightwithin two or more spectral ranges, in a first mode of operation, onlythe first set of light emitting devices are used, and in a second modeof operation, only the second set of light emitting devices are used.Here, it will be understood that the first set of light emitting devicesis a single first LED and the second set of light emitting devices is asingle second LED in some embodiments. The same or a similar arrangementof light emitting devices and bandpass filters may be used in otherlight sources of the imaging device 100. Of course, additional modes ofoperations (e.g., a third mode of operation, a fourth mode of operation,etc.) are also possible by including additional sets of light emittingdevices and/or additional bandpass filters corresponding to additionalspectral ranges.

In various implementations, as shown in FIG. 2B, the optical assembly102 has two light sources, including light source 106 and light source107. In various implementations, both light sources are configured toemit light falling within two substantially non-overlapping spectralranges. For example, in a first mode of operation, both light sources106 and 107 emit light within a spectral range of 500 nm to 600 nm (orany other appropriate spectral range), and in a second mode of operationboth light sources 106 and 107 emit light within a spectral range of 600nm to 700 nm (or any other appropriate spectral range).

In some implementations where the hyperspectral imaging device includestwo light sources (e.g., light sources 106 and 107), each light sourceis configured to emit light falling within only one of the twosubstantially non-overlapping spectral ranges. For example, in a firstmode of operation, light source 106 emits light within a first spectralrange (e.g., 500 nm to 600 nm, or any other appropriate spectral range),and in a second mode of operation, light source 107 emits light within asecond spectral range (e.g., 600 nm to 700 nm, or any other appropriatespectral range).

In some implementations where the hyperspectral imaging device includestwo light sources (e.g., light sources 106 and 107), each light sourceis configured to emit light falling within a corresponding predeterminedspectral range. For example, in a first mode of operation, light source106 emits light within a first spectral range (e.g., one thatencompasses 520 nm, 540 nm, 560 nm and 640 nm light), and in a secondmode of operation, light source 107 emits light within a second spectralrange (e.g. one that encompasses 580 nm, 590 nm, 610 nm and 620 nmlight).

In some embodiments the first and second modes of light operation applyto the pair of light sources. In other words, while each respectivelight source only emits light falling within one respective spectralrange, the pair of light sources together operate according to the firstand the second modes of operation described above.

In various implementations, one or both of the two substantiallynon-overlapping spectral ranges are non-contiguous spectral ranges. Forexample, a first light source may emit light having wavelengths between490 nm and 580 nm in a discontinuous fashion (e.g., in spectral bands of490-510 nm and 520-580 nm), and a second light source may emit lighthaving wavelengths between 575 nm and 640 in a continuous fashion (e.g.,in a single spectral band of 575-640 nm). In another example, a firstlight source may emit light having wavelengths between 510 nm and 650 nmin a discontinuous fashion (e.g., in spectral bands of 510-570 nm and630-650 nm), and a second light source may emit light having wavelengthsbetween 570 nm and 630 in a continuous fashion (e.g., in a singlespectral band of 570-630 nm). In still another example, a light source106 may emit light having wavelengths between 515 nm and 645 nm in adiscontinuous fashion (e.g., in spectral bands of 515-565 nm and 635-645nm), and light source 107 may emit light having wavelengths between 575nm and 625 in a continuous fashion (e.g., in a single spectral band of575-625 nm).

In some implementations, light sources 106 and 107 are broadband lightsources (e.g., white LEDs) covered by corresponding first and secondwavelength filters, having substantially overlapping pass bands. In someimplementations, light sources 106 and 107 are broadband light sources(e.g., white LEDs) covered by corresponding first and second wavelengthfilters, having substantially non-overlapping pass bands. The pass bandsof filters used in such implementations are based on the identity of thespectral bands to be imaged for creation of the hyperspectral data cube.

In one implementation, the spectral bands to be collected are separatedinto two groups. The first group consisting of spectral bands withwavelengths below a predetermined wavelength and the second groupconsisting of spectral bands with wavelengths above a predeterminedwavelength. For example, if images at eight spectral bands are needed tocreate a particular hyperspectral data cube, the four spectral bandshaving the shortest wavelengths make up the first group and the otherfour spectral bands make up the second group. The first pass band isthen selected such that the first filter allows light having wavelengthscorresponding to the first group, but blocks substantially all lighthaving wavelengths corresponding to the second group. Likewise thesecond pass band is selected such that the second filter allows lighthaving wavelengths corresponding to the second group, but blockssubstantially all light having wavelengths corresponding to the firstgroup.

In another implementation, the spectral bands to be collected areseparated into two groups. The first group consists of a first subset ofspectral bands and the second group consists of a second subset ofspectral bands. In this implementation, the division into the twosubsets is made in such a manner that, upon pairing a spectral band fromthe first subset with a spectral band from the second subset, a minimumpredetermined band separation is guaranteed. For instance, in oneembodiment the first subset comprises 520, 540, 560, and 640 whereas thesecond subset comprises 580, 590, 510 and 620. Moreover, four pairs ofwavelengths are formed, each pair comprising one band from the firstsubset and one band from the second subset, where the minimum separationbetween the paired bands is at least 50 nm. For example, in oneembodiment the following pairs are formed: pair (i) 520 nm/590 nm, pair(ii) 540 nm/610 nm, pair (iii) 560 nm/620 nm, and pair (iv) 580 nm/640nm. Advantageously, paired bands where the center of each band in thepair is at least 50 nm apart allows facilitates the effectiveness of thedual bandpass filters used to cover the photo-sensors in someembodiments, because the two wavelengths ranges that each such bandpassfilter permits to pass through are far enough apart from each other toensure filter effectiveness. Accordingly, in some implementations, dualpass band filters, allowing passage of one spectral band from the firstgroup and one spectral band from the second group, are placed in frontof each photo-sensor, such that one image is captured at a spectral bandbelonging to the first group (e.g., upon illumination of the object bylight source 106), and one image is captured at a spectral bandbelonging to the second group (e.g., upon illumination of the object bylight source 107).

In one implementation, where the hyperspectral data cube is used fordetermining the oxyhemoglobin and deoxyhemoglobin content of a tissue,the first filter has a pass band starting at between 430 and 510 nm andending between 570 nm and 590 nm, and the second filter has a pass bandstarting at between 570 nm and 580 nm and ending between 645 nm and 700nm.

In a first implementation, the imaging device 100 is configured tocollect a set of images, where each image in the set of images iscollected at a discrete spectral band, and the set of images comprisesimages collected at any 4 or more, any 5 or more, any six or more, anyseven or more, or all of the set of discrete spectral bands havingcentral wavelengths {510±5 nm, 530±5 nm, 540±5 nm, 560±5 nm, 580±5 nm,590±5 nm, 620±5 nm, and 660±5 nm}, where each respective spectral bandin the set has a full width at half maximum of less than 15 nm, lessthan 10 nm, or 5 nm or less. In some embodiments of this firstimplementation, a first bandpass filter, covering light source 106, hasa first pass band that permits wavelengths 500±5−550±5 nm and a secondpass band that permits wavelengths 650±5−670±5 nm while all otherwavelengths are blocked, and a second bandpass filter, covering lightsource 107, has a single pass band that permits wavelengths 550±5nm−630±5 nm while all other wavelengths are blocked. In other suchembodiments of this first implementation, a first bandpass filter,covering light source 106, has a first pass band that permitswavelengths 505±5−545±5 nm and a second pass band that permitswavelengths 655±5−665±5 nm while all other wavelengths are blocked, anda second bandpass filter, covering light source 107, has a single passband that permits wavelengths 555±5 nm−625±5 nm while all otherwavelengths are blocked.

In a second implementation, the imaging device 100 is configured tocollect a set of images, where each image in the set of images iscollected at a discrete spectral band, and the set of images comprisesimages collected at any four or more, any five or more, any six or more,any seven or more, or all of the set of discrete spectral bands havingcentral wavelengths {520±5 nm, 540±5 nm, 560±5 nm, 580±5 nm, 590±5 nm,610±5 nm, 620±5 nm, and 640±5 nm} where each respective spectral band inthe set has a full width at half maximum of less than 15 nm, less than10 nm, or 5 nm or less. In some embodiments of this secondimplementation, a first bandpass filter, covering light source 106, hasa first pass band that permits wavelengths 510±5−570±5 nm and a secondpass band that permits wavelengths 630±5−650±5 nm while all otherwavelengths are blocked, and a second bandpass filter, covering lightsource 107, has a single pass band that permits wavelengths 570±5nm−630±5 nm, while all other wavelengths are blocked. In other suchembodiments of this second implementation, a first bandpass filter,covering light source 106, has a first pass band that permitswavelengths 515±5−565±5 nm and a second pass band that permitswavelengths 635±5−645±5 nm while all other wavelengths are blocked, anda second bandpass filter, covering light source 107, has a single passband that permits wavelengths 575±5 nm−625±5 nm while all otherwavelengths are blocked.

In a third implementation, the imaging device 100 is configured tocollect a set of images, where each image in the set of images iscollected at a discrete spectral band, and the set of images comprisesimages collected at any four or more, any five or more, any six or more,any seven or more, or all of the set of discrete spectral bands havingcentral wavelengths {500±5 nm, 530±5 nm, 545±5 nm, 570±5 nm, 585±5 nm,600±5 nm, 615±5 nm, and 640±5 nm} where each respective spectral band inthe set has a full width at half maximum of less than 15 nm, less than10 nm, or 5 nm or less. In some embodiments of this thirdimplementation, a first bandpass filter, covering light source 106, hasa first pass band that permits wavelengths 490±5−555±5 nm and a secondpass band that permits wavelengths 630±5−650±5 nm while all otherwavelengths are blocked, and a second bandpass filter, covering lightsource 107, has a single pass band that permits wavelengths 560±5nm−625±5 nm, while all other wavelengths are blocked. In other suchembodiments of this third implementation, a first bandpass filter,covering light source 106, has a first pass band that permitswavelengths 495±5−550±5 nm and a second pass band that permitswavelengths 635±5−645±5 nm while all other wavelengths are blocked, anda second bandpass filter, covering light source 107, has a single passband that permits wavelengths 565±5 nm−620±5 nm while all otherwavelengths are blocked.

In some implementations, light sources 106 and 107 are broadband lightsources (e.g., white LEDs). First light source 106 is covered by a shortpass filter (e.g., a filter allowing light having wavelengths below acut-off wavelength to pass through while blocking light havingwavelengths above the cut-off wavelength) and second light source 107 iscovered by a long pass filter (e.g., a filter allowing light havingwavelengths above a cut-on wavelength to pass through while blockinglight having wavelengths below the cut-on wavelength). The cut-off andcut-on wavelengths of the short and long pass filters are determinedbased on the set of spectral bands to be captured by the imaging system.Generally, respective cut-off and cut-on wavelengths are selected suchthat they are longer than the longest wavelength to be captured in afirst set of images and shorter than the shortest wavelength to becaptured in a second set of images (e.g., where the first and second setof images are combined to form a hyperspectral data set).

For example, referring to FIG. 2B and FIG. 3, in one implementation,photo-sensors 210 are each covered by a dual pass band filter 216. Eachdual pass band filter 216 allows light of first and second spectralbands to pass through to the respective photo-sensor 210. Cut-off andcut-on wavelengths for filters covering light sources 106 and 107 areselected such that exactly one pass band from each filter 216 is belowthe cut-off wavelength of the filter covering light source 106 and theother pass band from each filter 216 is above the cut-on wavelength ofthe filter covering light source 107.

In one implementation, where the hyperspectral data cube is used fordetermining the oxyhemoglobin and deoxyhemoglobin content of a tissue,the cut-off wavelength of the short-pass filter covering light source106 and the cut-on wavelength of the long-pass filter covering lightsource 107 are between 565 nm and 585 nm.

In a first implementation, the hyperspectral imaging device isconfigured to collect images at spectral bands having centralwavelengths of 510±5 nm, 530±5 nm, 540±5 nm, 560±5 nm, 580±5 nm, 590±5nm, 620±5 nm, and 660±5 nm, where each respective spectral band has afull width at half maximum of less than 15 nm, and the cut-offwavelength of a short-pass filter covering light source 106 and cut-onwavelength of a long-pass filter covering light source 107 are eachindependently 570±5 nm.

In a second implementation, the hyperspectral imaging device isconfigured to collect images at spectral bands having centralwavelengths of 520±5 nm, 540±5 nm, 560±5 nm, 580±5 nm, 590±5 nm, 610±5nm, 620±5 nm, and 640±5 nm, where each respective spectral band has afull width at half maximum of less than 15 nm, and the cut-offwavelength of a short-pass filter covering light source 106 and cut-onwavelength of a long-pass filter covering light source 107 are eachindependently 585±5 nm.

In a third implementation, the hyperspectral imaging device isconfigured to collect images at spectral bands having centralwavelengths of 500±5 nm, 530±5 nm, 545±5 nm, 570±5 nm, 585±5 nm, 600±5nm, 615±5 nm, and 640±5, where each respective spectral band has a fullwidth at half maximum of less than 15 nm, and the cut-off wavelength ofa short-pass filter covering light source 106 and cut-on wavelength of along-pass filter covering light source 107 are each independently577.5±5 nm.

In various implementations, the imaging device 100 includes three ormore light sources (e.g., 2, 3, 4, 5, 6, or more light sources). In suchcases, any appropriate assignments of spectral ranges (or any otherdesired characteristic) among the three or more light sources may beused. For example, each light source can be configured to emit lightaccording to each mode of operation desired. Thus, for example, if foursubstantially non-overlapping spectral ranges are required from fourlight sources, each light source may be configured to emit light withineach of the four spectral ranges. In other cases, each respective lightsource may be configured to emit light within a different respective oneof the four spectral ranges. In yet other cases, two of the lightsources may be configured to emit light within each of two of the fourspectral ranges, and the other two light sources may be configured toemit light within each of the remaining two spectral ranges. Otherassignments of spectral ranges among the light sources are alsocontemplated.

With reference to FIG. 4, the optical assembly 102 also includes anoptical path assembly 204 that directs light received by the lensassembly 104 to a plurality of photo-sensors 210 (e.g., 210-1, . . .210-4) coupled to the first and the second circuit boards 206, 208. Inparticular, as described herein, the optical path assembly 204 includesa plurality of beam splitters 212 (e.g., 212-1 . . . 212-3) and aplurality of beam steering elements 214 (e.g., 214-2, 214-4). The beamsplitters 212 and the beam steering elements 214 are configured to splitthe light received by the lens assembly 104 into a plurality of opticalpaths, and direct those optical paths onto the plurality ofphoto-sensors 210 of the optical assembly 102.

Beam splitters of several different types may be used in the opticalassembly 102 in various implementations. One type of beam splitter thatis used in various implementations is configured to divide a beam oflight into two separate paths that each have substantially the samespectral content. For example, approximately 50% of the light incidenton the beam splitter is transmitted in a first direction, while theremaining approximately 50% is transmitted in a second direction (e.g.,perpendicular to the first direction). Other ratios of the lighttransmitted in the two directions may also be used in variousimplementations. For ease of reference, this type of beam splitter isreferred to herein as a 50:50 beam splitter, and is distinguished from adichroic beam splitter that divides a beam of light into to two separatepaths that each have a different spectral content. For example, adichroic beam splitter that receives light having a spectral range of450-650 nm (or more) may transmit light having a spectral range of450-550 nm in a first direction, and transmit light having a spectralrange of 550-650 nm in a second direction (e.g., perpendicular to thefirst direction).

In addition, other ranges may be utilized, including but not limited todiscontinuous spectral sub-ranges. For example, a first spectral rangeincludes a first spectral sub-range of about 450-550 nm and a secondspectral sub-range of about 615-650 nm, and second, third and fourthspectral ranges may be about 550-615 nm, 585-650 nm and 450-585 nm,respectively. Alternatively, various beam splitters may be utilized tosplit light into a first spectral range having a first spectralsub-range of about 450-530 nm and a second spectral sub-range of about600-650 nm, a second spectral range of about 530-600 nm, a thirdspectral range having at least two discontinuous spectral sub-rangesincluding a third spectral sub-range of about 570-600 nm and a fourthspectral sub-range of about 615-650 nm, a fourth spectral range havingat least two discontinuous spectral sub-ranges including a fifthspectral sub-range of about 450-570 nm and a sixth spectral sub-range ofabout 600-615 nm, at least two discontinuous spectral sub-ranges of afifth spectral range including a seventh spectral sub-range of about585-595 nm and an eighth spectral sub-range of about 615-625 nm, and atleast two discontinuous spectral sub-ranges of a sixth spectral rangeincluding a ninth spectral sub-range of about 515-525 nm and a tenthspectral sub-range of about 555-565 nm.

In various implementations, the beam splitters 212 are 50:50 beamsplitters. In various implementations, the beam splitters 212 aredichroic beam splitters (e.g., beam splitters that divide a beam oflight into separate paths that each have a different spectral content).In various implementations, the beam splitters 212 include a combinationof 50:50 beam splitters and dichroic beam splitters. Several specificexamples of optical assemblies 102 employing beam splitters of varioustypes are discussed herein.

The optical path assembly 204 is configured such that the image that isprovided to each of the photo-sensors (or, more particularly, thefilters that cover the photo-sensors) is substantially identical (e.g.,the same image is provided to each photo-sensor). Because thephoto-sensors 210 can all be operated simultaneously, the opticalassembly 102 is able to capture a plurality of images of the same objectat substantially the same time (thus capturing multiple images thatcorrespond to the same lighting conditions of the object). Moreover,because each photo-sensor 210-n is covered by a bandpass filter 216-nhaving a different passband, each photo-sensor 210-n captures adifferent spectral component of the image. These multiple images, eachrepresenting a different spectral component, are then assembled into ahyperspectral data cube for analysis.

In some embodiments, each photo-sensor 210-n is a pixel array. In someembodiments each photo-sensor 210-n comprises 500,000 pixels, 1,000,000pixels, 1,100,000 pixels, 1,200,000 pixels or more than 1,300,000pixels. In an exemplary embodiment a photo-sensor in the plurality ofphoto-sensors is a ½-inch megapixel CMOS digital image sensor such asthe MT9M001C12STM monochrome sensor (Aptina Imaging Corporation, SanJose, Calif.).

FIG. 3 is an exploded schematic view of the optical assembly 102, inaccordance with various implementations. FIG. 3 further illustrates thearrangement of the various components of the optical assembly. Inparticular, the optical assembly 102 includes a first circuit board 206and a second circuit board 208, where the first and second circuitboards 206, 208 are substantially parallel to one another and arepositioned on opposing sides of the optical path assembly 204. Invarious implementations, the circuit boards 206, 208 are rigid circuitboards.

Coupled to the first circuit board 206 are a first photo-sensor 210-1and a third photo-sensor 210-3. Coupled to the second circuit board 208are a second photo-sensor 210-2 and a fourth photo-sensor 210-4. Invarious implementations, the photo-sensors 210 are coupled directly totheir respective circuit boards (e.g., they are rigidly mounted to thecircuit board). In various implementations, in order to facilitateprecise alignment of the photo-sensors 210 with respect to the opticalpath assembly 204, the photo-sensors 210 are flexibly coupled to theirrespective circuit board. For example, in some cases, the photo-sensors210 are mounted on a flexible circuit (e.g., including a flexiblesubstrate composed of polyamide, PEEK, polyester, or any otherappropriate material). The flexible circuit is then electronicallycoupled to the circuit board 206, 208. In various implementations, thephoto-sensors 210 are mounted to rigid substrates that are, in turn,coupled to one of the circuit boards 206, 208 via a flexibleinterconnect (e.g., a flexible board, flexible wire array, flexible PCB,flexible flat cable, ribbon cable, etc.).

As noted above, the optical assembly 102 includes a plurality ofbandpass filters 216 (e.g., 216-1 . . . 216-4). The bandpass filters 216are positioned between the photo-sensors 210 and their respectiveoptical outlets of the optical path assembly 204. Thus, the bandpassfilters 216 are configured to filter the light that is ultimatelyincident on the photo-sensors 210. In some embodiments, each bandpassfilter 216 is a dual bandpass filter.

In various implementations, each bandpass filter 216 is configured tohave a different pass band. Accordingly, even though the optical pathassembly 204 provides the same image to each photo-sensor (or, moreparticularly, to the filters that cover the photo-sensors), eachphoto-sensor actually captures a different spectral component of theimage. For example, as discussed in greater detail herein, a firstbandpass filter 216-1 may have a passband centered around 520 nm, and asecond bandpass filter 216-2 may have a passband centered around 540 nm.Thus, when the imaging device 100 captures an exposure, the firstphoto-sensor 210-1 (which is filtered by the first bandpass filter216-1) will capture an image representing the portion of the incominglight having a wavelength centered around 520 nm, and the secondphoto-sensor 210-2 (which is filtered by the second bandpass filter216-2) will capture an image representing the portion of the incominglight having a wavelength around 540 nm. (As used herein, the termexposure refers to a single imaging operation that results in thesimultaneous or substantially simultaneous capture of multiple images onmultiple photo-sensors.) These images, along with the other imagescaptured by the third and fourth photo sensors 210-3, 210-4 (eachcapturing a different spectral band), are then assembled into ahyperspectral data cube for further analysis.

In various implementations, at least a subset of the bandpass filters216 are configured to allow light corresponding to two (or more)discrete spectral bands to pass through the filter. While such filtersmay be referred to herein as dual bandpass filters, this term is meantto encompass bandpass filters that have two discrete passbands as wellas those that have more than two discrete passbands (e.g., triple-bandbandpass filters, quadruple-band bandpass filters, etc.). By usingbandpass filters that have multiple passbands, each photo-sensor can beused to capture images representing several different spectral bands.For example, the hyperspectral imaging device 100 will first illuminatean object with light within a spectral range that corresponds to onlyone of the passbands of each of the bandpass filters, and capture anexposure under the first lighting conditions. Subsequently, thehyperspectral imaging device 100 will illuminate an object with lightwithin a spectral range that corresponds to a different one of thepassbands on each of the bandpass filters, and then capture an exposureunder the second lighting conditions. Thus, because the firstillumination conditions do not include any spectral content that wouldbe transmitted by the second passband, the first exposure results ineach photo-sensor capturing only a single spectral component of theimage. Conversely, because the second illumination conditions do notinclude any spectral content that would be transmitted by the firstpassband, the second exposure results in each photo-sensor capturingonly a single spectral component of the image.

As a more specific example, in various implementations, the bandpassfilters 216-1 through 216-4 each include one passband falling within therange of 500-585 nm, and a second passband falling within the range of585-650 nm, as shown below in table (1):

TABLE 1 Exemplary Central Eavelengths of Pass-bands for Filters216-1-216-4 Filter 216-1 Filter 216-2 Filter 216-3 Filter 216-4 Passband1 520 nm 540 nm 560 nm 580 nm Passband 2 590 nm 610 nm 620 nm 640 nm

In one implementation, the light source 106 has two modes of operation:in a first mode of operation, the light source 106 emits light havingwavelengths according to a first set of spectral bands (e.g., below 585nm, such as between 500 nm and 585 nm); in a second mode of operation,the light source 106 emits light having wavelengths according to asecond set of spectral bands (e.g., above 585 nm, such as between 585 nmand 650 nm). Thus, when the first exposure is captured using the firstillumination mode, four images are captured, where each imagecorresponds to a single spectral component of the incoming light.Specifically, the image captured by the first sensor 210-1 will includesubstantially only that portion of the incoming light falling within afirst passband (e.g., centered around 520 nm), the image captured by thesecond sensor 210-2 will include substantially only that portion of theincoming light falling within a second passband (e.g., centered around540 nm), and so on. When the second exposure is captured using thesecond illumination mode, four additional images are captured, whereeach image corresponds to a single spectral component of the incominglight. Specifically, the image captured by the first sensor 210-1 willinclude substantially only that portion of the incoming light fallingwithin the other pass band allowed by the dual band filter 216-1 (e.g.,centered around 590 nm), the image captured by the second sensor 210-2will include substantially only that portion of the incoming lightfalling within the other pass band allowed by dual band filter 216-2(e.g., centered around 610 nm), and so on. The eight images resultingfrom the two exposures described above are then assembled into ahyperspectral data cube for further analysis.

In another implementation, as illustrated in FIG. 2B, the hyperspectralimaging device has two light sources 106, 107, and each light source isconfigured to illuminate an object with a different set of spectralbands. The hyperspectral imaging device has two modes of operation: in afirst mode of operation, light source 106 emits light having wavelengthsaccording to a first set of spectral bands. In a second mode ofoperation, light source 107 emits light having wavelengths according toa second set of spectral bands. Thus, when the first exposure iscaptured using the first illumination mode, four images are captured,where each image corresponds to a single spectral component of theincoming light. Specifically, the image captured by the first sensor210-1 during the first mode of operation will include substantially onlythat portion of the incoming light falling within a first passband(e.g., centered around 520 nm), the image captured by the second sensor210-2 during the first mode of operation will include substantially onlythat portion of the incoming light falling within a second passband(e.g., centered around 540 nm), and so on. When the second exposure iscaptured using the second illumination mode, four additional images arecaptured, where each image corresponds to a single spectral component ofthe incoming light. Specifically, the image captured by the first sensor210-1 will include substantially only that portion of the incoming lightfalling within the other pass band allowed by the dual band filter 216-1(e.g., centered around 590 nm), the image captured by the second sensor210-2 will include substantially only that portion of the incoming lightfalling within the other pass band allowed by dual band filter 216-2(e.g., centered around 610 nm), and so on. The eight images resultingfrom the two exposures described above are then assembled into ahyperspectral data cube for further analysis. In typical embodiments,each such image is a multi-pixel image. In some embodiments, thisassembly involves combining each image in the plurality of images, on apixel by pixel basis, to form a composite image.

In the above examples, each filter 216-n has two passbands. However, invarious implementations, the filters do not all have the same number ofpassbands. For example, if fewer spectral bands need to be captured, oneor more of the filters 216-n may have only one passband. Similarly, oneor more of the filters 216-n may have additional passbands. In thelatter case, the light source 104 will have additional modes ofoperation, where each mode of operation illuminates an object with lightthat falls within only 1 (or none) of the passbands of each sensor.

FIG. 4 is an exploded schematic view of a portion of the opticalassembly 102, in accordance with various implementations, in which theoptical paths formed by the optical path assembly 204 are shown. Theoptical path assembly 204 channels light received by the lens assembly104 to the various photo-sensors 210 of the optical assembly 102.

Turning to FIG. 4, the optical assembly 102 includes a first beamsplitter 212-1, a second beam splitter 212-2, and a third beam splitter212-3. Each beam splitter is configured to split the light received bythe beam splitter into at least two optical paths. For example, beamsplitters for use in the optical path assembly 204 may split an incomingbeam into one output beam that is collinear to the input beam, andanother output beam that is perpendicular to the input beam.

Specifically, the first beam splitter 212-1 is in direct opticalcommunication with the lens assembly 104, and as shown in FIG. 10,splits the incoming light (represented by arrow 400) into a firstoptical path 401 and a second optical path 402. The first optical path401 is substantially collinear with the light entering the first beamsplitter 212-1, and passes to the second beam splitter 212-2. The secondoptical path 402 is substantially perpendicular to the light enteringthe first beam splitter 212-1, and passes to the third beam splitter212-3. In various implementations, the first beam splitter 212-1 is a50:50 beam splitter. In other implementations, the first beam splitter212-1 is a dichroic beam splitter.

With continued reference to FIG. 10, the second beam splitter 212-2 isadjacent to the first beam splitter 212-1 (and is in direct opticalcommunication with the first beam splitter 212-1), and splits theincoming light from the first beam splitter 212-1 into a third opticalpath 403 and a fourth optical path 404. The third optical path 403 issubstantially collinear with the light entering the second beam splitter212-2, and passes through to the first beam steering element 214-1 (seeFIG. 4). The fourth optical path is substantially perpendicular to thelight entering the second beam splitter 212-2, and passes through to thesecond beam steering element 214-2. In various implementations, thesecond beam splitter 212-2 is a 50:50 beam splitter. In otherimplementations, the second beam splitter 212-2 is a dichroic beamsplitter.

The beam steering elements 214 (e.g., 214-1 . . . 214-4 shown in FIG. 4)are configured to change the direction of the light that enters one faceof the beam steering element. Beam steering elements 214 are anyappropriate optical device that changes the direction of light. Forexample, in various implementations, the beam steering elements 214 areprisms (e.g., folding prisms, bending prisms, etc.). In variousimplementations, the beam steering elements 214 are mirrors. In variousimplementations, the beam steering elements 214 are other appropriateoptical devices or combinations of devices.

Returning to FIG. 4, the first beam steering element 214-1 is adjacentto and in direct optical communication with the second beam splitter212-2, and receives light from the third optical path (e.g., the outputof the second beam splitter 212-2 that is collinear with the input tothe second beam splitter 212-2). The first beam steering element 214-1deflects the light in a direction that is substantially perpendicular tothe fourth optical path (and, in various implementations, perpendicularto a plane defined by the optical paths of the beam splitters 212, e.g.,the x-y plane) and onto the first photo-sensor 210-1 coupled to thefirst circuit board 206 (FIG. 3). The output of the first beam steeringelement 214-1 is represented by arrow 411 (see FIG. 4).

The second beam steering element 214-2 is adjacent to and in directoptical communication with the second beam splitter 212-2, and receiveslight from the fourth optical path (e.g., the perpendicular output ofthe second beam splitter 212-2). The second beam steering element 214-2deflects the light in a direction that is substantially perpendicular tothe third optical path (and, in various implementations, perpendicularto a plane defined by the optical paths of the beam splitters 212, e.g.,the x-y plane) and onto the second photo-sensor 210-2 coupled to thesecond circuit board 208 (FIG. 3). The output of the second beamsteering element 214-2 is represented by arrow 412 (see FIG. 4).

As noted above, the first beam splitter 212-1 passes light to the secondbeam splitter 212-2 along a first optical path (as discussed above), andto the third beam splitter 212-3 along a second optical path.

With reference to FIG. 10, the third beam splitter 212-3 is adjacent tothe first beam splitter 212-1 (and is in direct optical communicationwith the first beam splitter 212-1), and splits the incoming light fromthe first beam splitter 212-1 into a fifth optical path 405 and a sixthoptical path 406. The fifth optical path 405 is substantially collinearwith the light entering the third beam splitter 212-3, and passesthrough to the third beam steering element 214-3 (see FIG. 4). The sixthoptical path is substantially perpendicular to the light entering thethird beam splitter 212-3, and passes through to the fourth beamsteering element 214-4. In various implementations, the third beamsplitter 212-3 is a 50:50 beam splitter. In other implementations, thethird beam splitter 212-3 is a dichroic beam splitter.

The third beam steering element 214-3 (see FIG. 4) is adjacent to and indirect optical communication with the third beam splitter 212-3, andreceives light from the fifth optical path (e.g., the output of thethird beam splitter 212-3 that is collinear with the input to the thirdbeam splitter 212-3). The third beam steering element 214-3 deflects thelight in a direction that is substantially perpendicular to the thirdoptical path (and, in various implementations, perpendicular to a planedefined by the optical paths of the beam splitters 212, e.g., the x-yplane) and onto the third photo-sensor 210-3 coupled to the firstcircuit board 206 (FIG. 3). The output of the third beam steeringelement 214-3 is represented by arrow 413 (see FIG. 4).

The fourth beam steering element 214-4 is adjacent to and in directoptical communication with the third beam splitter 212-3, and receiveslight from the sixth optical path (e.g., the perpendicular output of thethird beam splitter 212-3). The fourth beam steering element 214-4deflects the light in a direction that is substantially perpendicular tothe sixth optical path (and, in various implementations, perpendicularto a plane defined by the optical paths of the beam splitters 212, e.g.,the x-y plane) and onto the fourth photo-sensor 210-4 coupled to thesecond circuit board 208 (FIG. 3). The output of the fourth beamsteering element 214-4 is represented by arrow 414 (see FIG. 4).

As shown in FIG. 4, the output paths of the first and third beamsteering elements 214-1, 214-3 are in opposite directions than theoutput paths of the second and fourth beam steering elements 214-2,214-4. Thus, the image captured by the lens assembly 104 is projectedonto the photo-sensors mounted on the opposite sides of the imageassembly 102. However, the beam steering elements 212 need not facethese particular directions. Rather, any of the beam steering elements212 can be positioned to direct the output path of each beam steeringelement 212 in any appropriate direction. For example, in variousimplementations, all of the beam steering elements 212 direct light inthe same direction. In such cases, all of the photo-sensors may bemounted on a single circuit board (e.g., the first circuit board 206 orthe second circuit board 208, FIG. 3). Alternatively, in variousimplementations, one or more of the beam steering elements 212 directslight substantially perpendicular to the incoming light, but insubstantially the same plane defined by the optical paths of the beamsplitters 212 (e.g., within the x-y plane). In yet otherimplementations, one or more beam steering elements 214 are excludedfrom the imaging device, and the corresponding photo-sensors 210 arepositioned orthogonal to the plane defined by optical paths 400-1 to400-6.

FIG. 5A is a top schematic view of the optical assembly 102 and theoptical path assembly 204 in accordance with various implementations,and FIG. 10 is a two-dimensional schematic illustration of the opticalpaths within the optical path assembly 204. Although illustrated with asingle light source 106, this optical path assembly may also beimplemented using a second light source 107, as illustrated in FIG. 5C.Light from the lens assembly 104 enters the first beam splitter 210-1,as indicated by arrow 400. The first beam splitter 210-1 splits theincoming light (arrow 400) into a first optical path (arrow 401) that iscollinear to the incoming light (arrow 400). Light along the firstoptical path (arrow 401) is passed through to the second beam splitter210-2. The first beam splitter 210-1 also splits the incoming light(arrow 400) into a second optical path (arrow 402) that is perpendicularto the incoming light (arrow 400). Light along the second optical path(arrow 402) is passed through to the third beam splitter 210-3.

Light entering the second beam splitter 210-2 (arrow 402) is furthersplit into a third optical path (arrow 403) that is collinear with theincoming light (arrow 400 and/or arrow 402). Light along the thirdoptical path (arrow 403) is passed to the first beam steering element214-1 (see, e.g., FIG. 4), which steers the light onto the firstphoto-sensor 210-1. As discussed above, in various implementations, thefirst beam steering element 214-1 deflects the light in a direction thatis perpendicular to the light entering the second beam splitter and outof the plane defined by the beam splitters (e.g., in a positivez-direction, or out of the page, as shown in FIG. 5).

Light entering the second beam splitter 210-2 (arrow 402) is furthersplit into a fourth optical path (arrow 404) that is perpendicular tothe incoming light (arrow 400 and/or arrow 402). Light along the fourthoptical path (arrow 404) is passed to the second beam steering element214-2, which steers the light onto the second photo-sensor 210-2. Asdiscussed above, in various implementations, the second beam steeringelement 214-2 deflects the light in a direction that is perpendicular tothe light entering the second beam splitter and out of the plane definedby the beam splitters (e.g., in a negative z-direction, or into thepage, as shown in FIG. 5).

Light entering the third beam splitter 210-3 (arrow 402) is furthersplit into a fifth optical path (arrow 405) that is collinear with thelight incoming into the third beam splitter 210-3 (arrow 402). Lightalong the fifth optical path (arrow 405) is passed to the third beamsteering element 214-3 (see, e.g., FIG. 4), which steers the light ontothe third photo-sensor 210-3. As discussed above, in variousimplementations, the third beam steering element 214-3 deflects thelight in a direction that is perpendicular to the light entering thethird beam splitter and out of the plane defined by the beam splitters(e.g., in a positive z-direction, or out of the page, as shown in FIG.5).

Light entering the third beam splitter 210-3 (arrow 402) is furthersplit into a sixth optical path (arrow 406) that is perpendicular to thelight incoming into the third beam splitter 210-3 (arrow 402). Lightalong the sixth optical path (arrow 406) is passed to the fourth beamsteering element 214-4, which steers the light onto the fourthphoto-sensor 210-4. As discussed above, in various implementations, thefourth beam steering element 214-4 deflects the light in a directionthat is perpendicular to the light entering the third beam splitter andout of the plane defined by the beam splitters (e.g., in a negativez-direction, or into the page, as shown in FIG. 5).

FIG. 5B is a top schematic view of the optical assembly 102 and theoptical path assembly 204 in accordance with various implementations,and FIG. 12 is a two-dimensional schematic illustration of the opticalpaths within the optical path assembly 204. Although illustrated withtwo light sources 106, 107, the optical path may also be implementedwith a single light source, configured to operate in one or moreoperating modes (e.g., two operating modes as described herein).

Light from the lens assembly 104 enters the first beam splitter 220-1,as indicated by arrow 600. The first beam splitter 220-1 splits theincoming light (arrow 600) into a first optical path (arrow 601) that isperpendicular to the incoming light (arrow 600) and a second opticalpath (arrow 602) that is collinear to the incoming light (arrow 600).Light along the first optical path (arrow 601) is passed to a beamsteering element in similar manner described above, which steers thelight onto the third photo-sensor 210-3. As discussed above, in variousimplementations, the steering element deflects the light in a directionthat is perpendicular to the first optical path (arrow 601) and out ofthe plane (e.g., in a positive z-direction, or out of the page) towardthe third photo-sensor 210-3. Light along the second optical path (arrow602) is passed through to a second beam splitter 220-2.

The second beam splitter 220-2 splits the incoming light (arrow 602)into a third optical path (arrow 603) that is perpendicular to theincoming light (arrow 602) and a fourth optical path (arrow 604) that iscollinear to the incoming light (arrow 602). Light along the thirdoptical path (arrow 603) is passed to another beam steering element insimilar manner described above, which steers the light onto the secondphoto-sensor 210-2. As discussed above, in various implementations, thesteering element deflects the light in a direction that is perpendicularto the third optical path (arrow 603) and out of the plane (e.g., in anegative z-direction, or into the page) toward the second photo-sensor210-2. Light along the fourth optical path (arrow 604) is passed throughto a third beam splitter 220-3.

The third beam splitter 220-3 splits the incoming light (arrow 604) intoa fifth optical path (arrow 605) that is perpendicular to the incominglight (arrow 604) and a sixth optical path (arrow 606) that is collinearto the incoming light (arrow 604). Light along the fifth optical path(arrow 605) is passed to another beam steering element, which steers thelight onto the fourth photo-sensor 210-4. As discussed above, in variousimplementations, the steering element deflects the light in a directionthat is perpendicular to the firth optical path (arrow 605) and out ofthe plane (e.g., in a negative z-direction, or into the page) toward thefourth photo-sensor 210-4. Light along the sixth optical path (arrow606) is passed to another beam steering element, which steers the lightonto the first photo-sensor 210-1. As discussed above, in variousimplementations, the steering element deflects the light in a directionthat is perpendicular to the sixth optical path (arrow 606) and out ofthe plane (e.g., in a positive z-direction, or out of the page) towardthe first photo-sensor 210-1.

FIG. 6 is a front schematic view of the optical assembly 102, inaccordance with various implementations. For clarity, the lens assembly104 and light source 106 are not shown. The lines within the beamsplitters 212 and the beam steering elements 214 further depict thelight paths described herein. For example, the line designated by arrow404 illustrates how the beam steering element 214-2 deflects the lightreceived from the beam splitter 212-2 onto the photo-sensor 210-2.Further, the line designated by arrow 402 illustrates how the beamsteering element 214-3 deflects the light received from the beamsplitter 212-3 onto the photo-sensor 210-3. Arrows 411-414(corresponding to the optical paths indicated in FIG. 4) furtherillustrate how the beam steering elements 214 direct light to theirrespective photo-sensors 210.

In the instant application, the geometric terms such as parallel,perpendicular, orthogonal, coplanar, collinear, etc., are understood toencompass orientations and/or arrangements that substantially satisfythese geometric relationships. For example, when a beam steering elementdeflects light perpendicularly, it is understood that the beam steeringelement may deflect the light substantially perpendicularly. As a morespecific example, in some cases, light may be determined to beperpendicular (or substantially perpendicular) when the light isdeflected 90+/−1 degrees from its input path. Other deviations fromexact geometric relationships are also contemplated.

As noted above, the optical assembly 102 can use various combinations of50:50 beam splitters and dichroic beam splitters. In a first example,the first beam splitter 212-1, the second beam splitter 212-2, and thethird beam splitter 212-3 are all 50:50 beam splitters. An exampleoptical assembly 102 with this selection of beam splitters isillustrated in FIG. 10.

In a second example, the first beam splitter 212-1 is a dichroic beamsplitter, and the second beam splitter 212-2 and the third beam splitter212-3 are both 50:50 beam splitters. An example optical assembly 102with this selection of beam splitters is illustrated in FIG. 11.

In a third example, the first beam splitter 212-1, the second beamsplitter 212-2, and the third beam splitter 212-3 are all dichroic beamsplitters. An example optical assembly 102 with this selection of beamsplitters is illustrated in FIG. 12.

FIG. 7 is a cutaway view of an implementation of imaging device 100,illustrating light paths 410 and 411, corresponding to light emittedfrom light source 106 and illuminating the object being imaged, as wellas light path 400, corresponding to light backscattered from the object.

The use of polarized illumination is advantageous because it eliminatessurface reflection from the skin and helps to eliminate stray lightreflection from off axis imaging directions. Accordingly, in variousimplementations, polarized light is used to illuminate the object beingimaged. In various implementations, the light is polarized with respectto a coordinate system relating to the plane of incidence formed by thepropagation direction of the light (e.g., the light emitted by lightsource 106) and a vector perpendicular to the plane of the reflectingsurface (e.g., the object being imaged). The component of the electricfield parallel to the plane of incidence is referred to as thep-component and the component perpendicular to the plane is referred toas the s-component. Accordingly, polarized light having an electricfield along the plane of incidence is “p-polarized,” while polarizedlight having an electric field normal to the plane is “s-polarized.”

Light can be polarized by placing a polarization filter in the path ofthe light. The polarizer allows light having the same polarization(e.g., p-polarized or s-polarized) to pass through, while reflectinglight having the opposite polarization. Because the polarizer ispassively filtering the incident beam, 50% of non-polarized light islost due to reflection off the polarizing filter. In practice,therefore, a non-polarized light source must produce twice the desiredamount of polarized illuminating light, at twice the power consumption,to account for this loss. Advantageously, in various implementations,the imaging device recaptures and reverses the polarity light reflectedoff the polarization filter, using a polarization rotator (e.g., apolarization rotation mirror). In various implementations, at least 95%of all of the light received by the polarizer from the at least onelight source may be illuminated onto the object.

Returning to FIG. 7, in one implementation, light emitted from lightsource 106 along optical path 410 is received by polarizer 700. Theportion of the light having the same polarization as polarizer 700(e.g., s- or p-polarization) passes through polarizer 700 and isdirected, through optical window 114, onto the surface of the object.The portion of the light having the opposite polarization as polarizer700 is reflected orthogonally along optical path 411, directed topolarization rotator 702. Polarization rotator 700 reverses thepolarization of the light (e.g., reverses the polarization to match thepolarization transmitted through polarizer 700) and reflects the light,through optical window 114, onto the surface of the object. Polarizedlight backscattered from the object, returning along optical path 400,is captured by lens assembly 104 and is directed internal to opticalassembly 102 as described above.

In this fashion, accounting for incidental loss of light along theoptical path, substantially all the light emitted from light source 106is projected onto the surface of the object being imaged in a polarizedmanner. This eliminates the need for light source 106 to produce twicethe desired amount illuminating light, effectively reducing the powerconsumption from illumination by 50%.

FIGS. 9A-9C are illustrations of framing guides projected onto thesurface of an object for focusing an image collected by animplementation of an imaging device 100.

As noted above, in various implementations, the lens assembly 104 has afixed focal distance. Thus, images captured by the imaging device 100will only be in focus if the imaging device 110 is maintained at anappropriate distance from the object to be imaged. In variousimplementations, the lens assembly 104 has a depth of field of a certainrange, such that objects falling within that range will be suitablyfocused. For example, in various implementations, the focus distance ofthe lens assembly 104 is 24 inches, and the depth of field is 3 inches.Thus, objects falling anywhere from 21 to 27 inches away from the lensassembly 104 will be suitably focused. These values are merelyexemplary, and other focus distances and depths of field are alsocontemplated.

Referring to FIG. 8A-8B, to facilitate accurate positioning of theimaging device 100 with respect to the object to be imaged, the dockingstation 110 includes first and second projectors 112 (e.g., 112-1,112-2) configured to project light (e.g., light 901, 903 in FIGS. 8A and8B, respectively) onto the object indicating when the imaging device 100is positioned at an appropriate distance from the object to acquire afocused image. In various implementations, with reference to FIGS.9A-9C, the first projector 112-1 and the second projector 112-2 areconfigured to project a first portion 902-1 and a second portion 902-2of a shape 902 onto the object (FIGS. 9A-9C), respectively. The firstportion of the shape 902-1 and the second portion of the shape 902-1 areconfigured to converge to form the shape 902 when the lens 104 ispositioned at a predetermined distance from the object, thepredetermined distance corresponding to a focus distance of the lens.

In one implementation, the framing guides converge to form a closedrectangle on the surface of the object when the lens of the imagingdevice 100 is positioned at predetermined distance from the objectcorresponding to the focus distance of the lens (FIG. 9C). When the lensof the imaging device 100 is positioned at distance from the object thatis less than the predetermined distance, the framing guides remainseparated (FIG. 9A). When the lens of the imaging device 100 ispositioned at distance from the object that is greater than thepredetermined distance, the framing guides cross each other (FIG. 9B).

In various implementations, the framing guides represent all orsubstantially all the area of the object that will be captured by theimaging device 100. In various implementations, at least all of theobject that falls inside the framing guides will be captured by theimaging device 100.

In various implementations, as illustrated in FIG. 8B, first projector112-1 and second projector 112-2 are each configured to project a spotonto the object (e.g., spots 904-1 and 904-2, illustrated in FIG. 9D),such that the spots converge (e.g., at spot 904 in FIG. 9E) when thelens 104 is positioned at a predetermined distance from the object, thepredetermined distance corresponding to a focus distance of the lens.When the lens of the imaging device 100 is positioned at distance fromthe object that is less than or greater than the predetermined distance,the projected spots diverge from each other (FIG. 9D).

FIG. 1B illustrates another imaging device 100, in accordance withvarious implementations, similar to that shown in FIG. 1A but includingan integrated body 101 that resembles a digital single-lens reflex(DSLR) camera in that the body has a forward-facing lens assembly 104,and a rearward facing display 122. The DSLR-type housing allows a userto easily hold imaging device 100, aim it toward a patient and theregion of interest (e.g., the skin of the patient), and position thedevice at an appropriate distance from the patient. One will appreciatethat the implementation of FIG. 1B, may incorporate the various featuresdescribed above and below in connection with the device of FIG. 1A.

In various implementations, and similar to the device described above,the imaging device 100 illustrated in FIG. 1B includes an opticalassembly having light sources 106 and 107 for illuminating the surfaceof an object (e.g., the skin of a subject) and a lens assembly 104 forcollecting light reflected and/or back scattered from the object.

In various implementations, and also similar to the device describedabove, the imaging device of FIG. 1B includes first and secondprojectors 112-1 and 112-2 configured to project light onto the objectindicating when the imaging device 100 is positioned at an appropriatedistance from the object to acquire a focused image. As noted above,this may be particularly useful where the lens assembly 104 has a fixedfocal distance, such that the image cannot be brought into focus bymanipulation of the lens assembly. As shown in FIG. 1B, the projectorsare mounted on a forward side of body 101.

In various implementations, the body 101 substantially encases andsupports the light sources 106 and 107 and the lens assembly 104 of theoptical assembly, along with the first and second projectors 112-1 and112-2 and the display 122.

FIGS. 13 and 14 collectively illustrate another configuration forimaging device 100, in accordance with various implementations, similarto that shown in FIG. 1B but including more detail regarding anembodiment of integrated body 101 and forward-facing lens assembly 104,and a rearward facing display 122. The housing 101 allows a user toeasily hold imaging device 100, aim it toward a patient and the regionof interest (e.g., the skin of the patient), and position the device atan appropriate distance from the patient. One will appreciate that theimplementation of FIGS. 13 and 14 may incorporate the various featuresdescribed herein in connection with the device of FIGS. 1A and 1B.

In various implementations, and similar to the device described above,the imaging device 100 illustrated in FIGS. 13 and 14 includes anoptical assembly having light sources 106 and 107 for illuminating thesurface of an object (e.g., the skin of a subject) and a lens assembly104 for collecting light reflected and/or back scattered from theobject.

In various implementations, and also similar to the device described inFIGS. 1A and 1B, the imaging device of FIG. 13 includes first and secondprojectors 112-1 and 112-2 configured to project light onto the objectindicating when the imaging device 100 is positioned at an appropriatedistance from the object to acquire a focused image. As noted above,this may be particularly useful where the lens assembly 104 has a fixedfocus distance, such that the image cannot be brought into focus bymanipulation of the lens assembly. As shown in FIG. 13, the projectorsare mounted on a forward side of body 101.

In various implementations, the body 101 substantially encases andsupports the light sources 106 and 107 and the lens assembly 104 of theoptical assembly, along with the first and second projectors 112-1 and112-2. In various implementations, the imaging device 101 of FIG. 13includes a live-view camera 103 and a remote thermometer 105.

Exemplary Optical Configurations

In one implementation, the imaging device 100 is configured to detect aset of spectral bands suitable for determining the oxyhemoglobin anddeoxyhemoglobin distribution in a tissue. In a specific implementation,this is achieved by capturing images of the tissue of interest at eightdifferent spectral bands. The images are captured in two exposures offour photo-sensors 210, each photo-sensor covered by a unique dual bandpass filter 216. In one implementation, the imaging device 100 has afirst light source 106 configured to illuminate the tissue of interestwith light including exactly four of the eight spectral bands, whereeach dual band pass filter 216 has exactly one pass band matching aspectral band in the four spectral bands emitted from light source 106.The imaging device has a second light source 107 configured toilluminate the tissue of interest with light including the other fourspectral bands of the set of eight spectral bands (e.g., but not thefirst four spectral bands), where each dual band pass filter 216 hasexactly one pass band matching a spectral band in the four spectralbands emitted from light source 107.

In one implementation, the set of eight spectral bands includes spectralbands having central wavelengths of: 510±5 nm, 530±5 nm, 540±5 nm, 560±5nm, 580±5 nm, 590±5 nm, 620±5 nm, and 660±5 nm, and each spectral bandhas a full width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510±4 nm, 530±4 nm, 540±4 nm, 560±4 nm,580±4 nm, 590±4 nm, 620±4 nm, and 660±4 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510±3 nm, 530±3 nm, 540±3 nm, 560±3 nm,580±3 nm, 590±3 nm, 620±3 nm, and 660±3 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510±2 nm, 530±2 nm, 540±2 nm, 560±2 nm,580±2 nm, 590±2 nm, 620±2 nm, and 660±2 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510±1 nm, 530±1 nm, 540±1 nm, 560±1 nm,580±1 nm, 590±1 nm, 620±1 nm, and 660±1 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510 nm, 530 nm, 540 nm, 560 nm, 580 nm,590 nm, 620 nm, and 660 nm, and each spectral band has a full width athalf maximum of about 10 nm.

In one implementation, dual band filters having spectral pass bandscentered at: (i) 520±5 and 590±5, (ii) 540±5 and 610±5, (iii) 560±5 and620±5, and (iv) 580±5 and 640±5 are placed in front of photo-sensorsconfigured to detect this particular set of wavelengths. In oneimplementation, the imaging device has a light source 106 configured toilluminate a tissue of interest with light having wavelengths from450-585 nm in a first operation mode and light having wavelengths from585-650 nm in a second operation mode. In one implementation, theimaging device has a light source 106 configured to illuminate a tissueof interest with light having wavelengths from 450-585 nm, and a secondlight source 107 configured to illuminate the tissue of interest withlight having wavelengths from 585-650 nm. In still anotherimplementation, the imaging device has a light source 106 configured toilluminate a tissue of interest with light having wavelengths 520, 540,560 and 640 but not wavelengths 580, 590, 610 and 620 and a second lightsource 107 configured to illuminate the tissue of interest with lighthaving wavelengths 580, 590, 610, and 620 but not wavelengths 520, 540,560 and 640.

In one implementation, dual band filters having spectral pass bandscentered at: (i) 520±5 and 560±5, (ii) 540±5 and 580±5, (iii) 590±5 and620±5, and (iv) 610 and 640±5 are placed in front of photo-sensorsconfigured to detect this particular set of wavelengths. In oneimplementation, the imaging device has a light source 106 configured toilluminate a tissue of interest with light having wavelengths from450-550 nm and from 615-650 nm in a first operation mode and lighthaving wavelengths from 550-615 nm in a second operation mode. In oneimplementation, the imaging device has a light source 106 configured toilluminate a tissue of interest with light having wavelengths from450-550 nm and from 615-650 nm, and a second light source 107 configuredto illuminate the tissue of interest with light having wavelengths from585-650 nm.

In one implementation, dual band filters having spectral pass bandscentered at: (i) 520±5 and 560±5, (ii) 540±5 and 610±5, (iii) 590±5 and620±5, and (iv) 580 and 640±5 are placed in front of photo-sensorsconfigured to detect this particular set of wavelengths. In oneimplementation, the imaging device has a light source 106 configured toilluminate a tissue of interest with light having wavelengths from450-530 nm and from 600-650 nm in a first operation mode and lighthaving wavelengths from 530-600 nm in a second operation mode. In oneimplementation, the imaging device has a light source 106 configured toilluminate a tissue of interest with light having wavelengths from450-530 nm and from 600-650 nm, and a second light source 107 configuredto illuminate the tissue of interest with light having wavelengths from530-600.

In one implementation, the set of eight spectral bands includes spectralbands having central wavelengths of: 520±5 nm, 540±5 nm, 560±5 nm, 580±5nm, 590±5 nm, 610±5 nm, 620±5 nm, and 640±5 nm, and each spectral bandhas a full width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520±4 nm, 540±4 nm, 560±4 nm, 580±4 nm,590±4 nm, 610±4 nm, 620±4 nm, and 640±4 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520±3 nm, 540±3 nm, 560±3 nm, 580±3 nm,590±3 nm, 610±3 nm, 620±3 nm, and 640±3 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520±2 nm, 540±2 nm, 560±2 nm, 580±2 nm,590±2 nm, 610±2 nm, 620±2 nm, and 640±2 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520±1 nm, 540±1 nm, 560±1 nm, 580±1 nm,590±1 nm, 610±1 nm, 620±1 nm, and 640±1 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520 nm, 540 nm, 560 nm, 580 nm, 590 nm,610 nm, 620 nm, and 640 nm, and each spectral band has a full width athalf maximum of about 10 nm.

In one implementation, the set of eight spectral bands includes spectralbands having central wavelengths of: 500±5 nm, 530±5 nm, 545±5 nm, 570±5nm, 585±5 nm, 600±5 nm, 615±5 nm, and 640±5 nm, and each spectral bandhas a full width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500±4 nm, 530±4 nm, 545±4 nm, 570±4 nm,585±4 nm, 600±4 nm, 615±4 nm, and 640±4 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500±3 nm, 530±3 nm, 545±3 nm, 570±3 nm,585±3 nm, 600±3 nm, 615±3 nm, and 640±3 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500±2 nm, 530±2 nm, 545±2 nm, 570±2 nm,585±2 nm, 600±2 nm, 615±2 nm, and 640±2 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500±1 nm, 530±1 nm, 545±1 nm, 570±1 nm,585±1 nm, 600±1 nm, 615±1 nm, and 640±1 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500 nm, 530 nm, 545 nm, 570 nm, 585 nm,600 nm, 615 nm, and 640 nm, and each spectral band has a full width athalf maximum of about 10 nm.

In other implementations, the imaging devices described here areconfigured for imaging more or less than eight spectral bands. Forexample, in some implementations, the imaging device is configured forimaging 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,21, 22, 23, 24, or more spectral bands. For example, imaging devicesincluding 7 beam splitters and 8 photo-sensors can be configuredaccording to the principles described herein to capture 8 imagessimultaneously, 16 images in two exposures (e.g., by placing dual bandpass filters in from of each photosensor), and 24 images in threeexposures (e.g., by placing triple band pass filters in front of eachphotosensor). In fact, the number of spectral band passes that can beimaged using the principles disclosed herein is only constrained by anydesired size of the imager, desired exposure times, and light sourcesemployed. Of course, one or more photo-sensors may not be used in anygiven exposure. For example, in a imaging device employing four photosensors and three beam splitters, seven images can be captured in twoexposures by not utilizing one of the photo-sensors in one of theexposures. Thus, imaging devices employing any combination of lightsources (e.g., 1, 2, 3, 4, or more), beam splitters (e.g., 1, 2, 3, 4,5, 6, 7, or more), and photo-sensors (e.g., 1, 2, 3, 4, 5, 6, 7, 8, ormore) are contemplated.

Optimization of Exposure Time

Many advantages of the imaging systems and methods described herein arederived, at least in part, from the use of in-band illumination anddetection across multiple spectral bands. For example, in-bandillumination allows for greater signal-to-noise ratio and reducedexposure times, which in turn results in lower power consumption,reduced misalignment due to movement of the subject, and reducedcomputational burden when processing the resulting hyperspectral datacubes.

These advantages can be further enhanced by minimizing the exposure time(e.g., shutter speed) needed to provide a suitable signal-to-noise ratioat each wavelength imaged. The minimum exposure time needed to resolve asuitable image at each wavelength will depend upon, at least, thesensitivity of the optical detector for the particular wavelength, thecharacteristics and intensity of ambient light present when acquiringimages, and the concentration of melanin in the skin/tissue beingimaged.

In one embodiment, the imaging systems described herein advantageouslyreduces the total amount of time required to collect a complete imageseries by determining the specific exposure time needed to resolve eachsub-image of the image series. Each image in the image series iscollected at a different spectral band and, because of this, the amountof time needed to resolve each sub-image will vary as a function ofwavelength. In some embodiments, this variance is advantageously takeninto account so that an image requiring less time, because of theiracquisition wavelengths or wavelength bands, are allotted shorterexposure times whereas images that require more time because of theiracquisition wavelengths or wavelength bands, are allotted shorterexposure times. This novel improvement affords a faster overall exposuretime because each of images in the series of images is only allocated anamount of time needed for full exposure, rather than a “one size fitsall” exposure time. This also reduces the power requirement of theimaging device, because the illumination, which requires a large amountof power, is shortened. In a specific embodiment, non-transitoryinstructions encoded by the imager in non-transient memory determine theminimal exposure time required for image acquisition at each spectralband acquired by the imaging system.

In some embodiments, the methods and systems described herein includeexecutable instructions for identifying a plurality of baseline exposuretimes, each respective baseline exposure time in the plurality ofbaseline exposure times representing an exposure time for resolving arespective image, in the series of images of the tissue being collected.A first baseline exposure time for a first image is different than asecond baseline exposure time of a second image in the plurality ofimages.

In one embodiment, a method is provided for acquiring an image series ofa tissue of a patient, including selecting a plurality of spectral bandsfor acquiring an image series of a tissue, identifying minimum exposuretimes for resolving an image of the tissue at each spectral band,identifying at least one factor affecting one of more minimum exposuretimes, adjusting the minimum exposure times based on the identifiedfactors, and acquiring a series of images of the tissue using theadjusted minimum exposure times.

In some embodiments, the minimum exposure times are based on baselineillumination of the tissue and/or the sensitivity of an optical detectoracquiring the image.

In some embodiments, the factor affecting the minimal exposure time isone or more of illumination provided by a device used to acquire theimage series, ambient light, and concentration of melanin in the tissue.

Hyperspectral Imaging

Hyperspectral and multispectral imaging are related techniques in largerclass of spectroscopy commonly referred to as spectral imaging orspectral analysis. Typically, hyperspectral imaging relates to theacquisition of a plurality of images, each image representing a narrowspectral band collected over a continuous spectral range, for example, 5or more (e.g., 5, 10, 15, 20, 25, 30, 40, 50, or more) spectral bandshaving a FWHM bandwidth of 1 nm or more each (e.g., 1 nm, 2 nm, 3 nm, 4nm, 5 nm, 10 nm, 20 nm or more), covering a contiguous spectral range(e.g., from 400 nm to 800 nm). In contrast, multispectral imagingrelates to the acquisition of a plurality of images, each imagerepresenting a narrow spectral band collected over a discontinuousspectral range.

For the purposes of the present disclosure, the terms “hyperspectral”and “multispectral” are used interchangeably and refer to a plurality ofimages, each image representing a narrow spectral band (having a FWHMbandwidth of between 10 nm and 30 nm, between 5 nm and 15 nm, between 5nm and 50 nm, less than 100 nm, between 1 and 100 nm, etc.), whethercollected over a continuous or discontinuous spectral range. Forexample, in various implementations, wavelengths 1-N of a hyperspectraldata cube 1336-1 are contiguous wavelengths or spectral bands covering acontiguous spectral range (e.g., from 400 nm to 800 nm). In otherimplementations, wavelengths 1-N of a hyperspectral data cube 1336-1 arenon-contiguous wavelengths or spectral bands covering a non-contiguousspectral ranges (e.g., from 400 nm to 440 nm, from 500 nm to 540 nm,from 600 nm to 680 nm, and from 900 to 950 nm).

As used herein, “narrow spectral range” refers to a continuous span ofwavelengths, typically consisting of a FWHM spectral band of no morethan about 100 nm. In certain embodiments, narrowband radiation consistsof a FWHM spectral band of no more than about 75 nm, 50 nm, 40 nm, 30nm, 25 nm, 20 nm, 15 nm, 10 nm, 5 nm, 4 nm, 3 nm, 2 nm, 1 nm, or less.In various implementations, wavelengths imaged by the methods anddevices disclosed herein are selected from one or more of the visible,near-infrared, short-wavelength infrared, mid-wavelength infrared,long-wavelength infrared, and ultraviolet (UV) spectrums.

By “broadband” it is meant light that includes component wavelengthsover a substantial portion of at least one band, for example, over atleast 20%, or at least 30%, or at least 40%, or at least 50%, or atleast 60%, or at least 70%, or at least 80%, or at least 90%, or atleast 95% of the band, or even the entire band, and optionally includescomponent wavelengths within one or more other bands. A “white lightsource” is considered to be broadband, because it extends over asubstantial portion of at least the visible band. In certainembodiments, broadband light includes component wavelengths across atleast 100 nm of the electromagnetic spectrum. In other embodiments,broadband light includes component wavelengths across at least 150 nm,200 nm, 250 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, or moreof the electromagnetic spectrum.

By “narrowband” it is meant light that includes components over only anarrow spectral region, for example, less than 20%, or less than 15%, orless than 10%, or less than 5%, or less than 2%, or less than 1%, orless than 0.5% of a single band. Narrowband light sources need not beconfined to a single band, but can include wavelengths in multiplebands. A plurality of narrowband light sources may each individuallygenerate light within only a small portion of a single band, buttogether may generate light that covers a substantial portion of one ormore bands, for example, may together constitute a broadband lightsource. In certain embodiments, broadband light includes componentwavelengths across no more than 100 nm of the electromagnetic spectrum(e.g., has a spectral bandwidth of no more than 100 nm). In otherembodiments, narrowband light has a spectral bandwidth of no more than90 nm, 80 nm, 75 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 25 nm, 20 nm, 15nm, 10 nm, 5 nm, or less of the electromagnetic spectrum.

As used herein, the “spectral bandwidth” of a light source refers to thespan of component wavelengths having an intensity that is at least halfof the maximum intensity, otherwise known as “full width at halfmaximum” (FWHM) spectral bandwidth. Many light emitting diodes (LEDs)emit radiation at more than a single discreet wavelength, and are thusnarrowband emitters. Accordingly, a narrowband light source can bedescribed as having a “characteristic wavelength” or “centerwavelength,” for example, the wavelength emitted with the greatestintensity, as well as a characteristic spectral bandwidth, for example,the span of wavelengths emitted with an intensity of at least half thatof the characteristic wavelength.

By “coherent light source” it is meant a light source that emitselectromagnetic radiation of a single wavelength in phase. Thus, acoherent light source is a type of narrowband light source with aspectral bandwidth of less than 1 nm. Non-limiting examples of coherentlight sources include lasers and laser-type LEDs. Similarly, anincoherent light source emits electromagnetic radiation having aspectral bandwidth of more than 1 nm and/or is not in phase. In thisregard, incoherent light can be either narrowband or broadband light,depending on the spectral bandwidth of the light.

Examples of suitable broadband light sources 106 include, withoutlimitation, incandescent lights such as a halogen lamp, xenon lamp, ahydrargyrum medium-arc iodide lamp, and a broadband light emitting diode(LED). In some embodiments, a standard or custom filter is used tobalance the light intensities at different wavelengths to raise thesignal level of certain wavelength or to select for a narrowband ofwavelengths. Broadband illumination of a subject is particularly usefulwhen capturing a color image of the subject or when focusing thehyperspectral/multispectral imaging system.

Examples of suitable narrowband, incoherent light sources 106 include,without limitation, a narrow band light emitting diode (LED), asuperluminescent diode (SLD) (see, Redding, B. et al, “Speckle-freelaser imaging”, arVix: 1110.6860 (2011), the content of which is herebyincorporated herein by reference in its entirety for all purposes), arandom laser, and a broadband light source covered by a narrow band-passfilter. Examples of suitable narrowband, coherent light sources 104include, without limitation, lasers and laser-type light emittingdiodes. While both coherent and incoherent narrowband light sources 104can be used in the imaging systems described herein, coherentillumination is less well suited for full-field imaging due to speckleartifacts that corrupt image formation (see, Oliver, B. M., “Sparklingspots and random diffraction”, Proc IEEE 51, 220-221 (1963)).

Hyperspectral Medical Imaging

Various implementations of the present disclosure provide for systemsand methods useful for hyperspectral/multispectral medical imaging(HSMI). HSMI relies upon distinguishing the interactions that occurbetween light at different wavelengths and components of the human body,especially components located in or just under the skin. For example, itis well known that deoxyhemoglobin absorbs a greater amount of light at700 nm than does water, while water absorbs a much greater amount oflight at 1200 nm, as compared to deoxyhemoglobin. By measuring theabsorbance of a two-component system consisting of deoxyhemoglobin andwater at 700 nm and 1200 nm, the individual contribution ofdeoxyhemoglobin and water to the absorption of the system, and thus theconcentrations of both components, can readily be determined Byextension, the individual components of more complex systems (e.g.,human skin) can be determined by measuring the absorption of a pluralityof wavelengths of light reflected or backscattered off of the system.

The particular interactions between the various wavelengths of lightmeasured by hyperspectral/multispectral imaging and each individualcomponent of the system (e.g., skin) produceshyperspectral/multispectral signature, when the data is constructed intoa hyperspectral/multispectral data cube. Specifically, different regions(e.g., different regions of interest or ROI on a single subject ordifferent ROIs from different subjects) interact differently with lightdepending on the presence of, e.g., a medical condition in the region,the physiological structure of the region, and/or the presence of achemical in the region. For example, fat, skin, blood, and flesh allinteract with various wavelengths of light differently from one another.A given type of cancerous lesion interacts with various wavelengths oflight differently from normal skin, from non-cancerous lesions, and fromother types of cancerous lesions. Likewise, a given chemical that ispresent (e.g., in the blood, or on the skin) interacts with variouswavelengths of light differently from other types of chemicals. Thus,the light obtained from each illuminated region of a subject has aspectral signature based on the characteristics of the region, whichsignature contains medical information about that region.

The structure of skin, while complex, can be approximated as twoseparate and structurally different layers, namely the epidermis anddermis. These two layers have very different scattering and absorptionproperties due to differences of composition. The epidermis is the outerlayer of skin. It has specialized cells called melanocytes that producemelanin pigments. Light is primarily absorbed in the epidermis, whilescattering in the epidermis is considered negligible. For furtherdetails, see G. H. Findlay, “Blue Skin,” British Journal of Dermatology83(1), 127-134 (1970), the content of which is incorporated herein byreference in its entirety for all purposes.

The dermis has a dense collection of collagen fibers and blood vessels,and its optical properties are very different from that of theepidermis. Absorption of light of a bloodless dermis is negligible.However, blood-born pigments like oxy- and deoxyhemoglobin and water aremajor absorbers of light in the dermis. Scattering by the collagenfibers and absorption due to chromophores in the dermis determine thedepth of penetration of light through skin.

Light used to illuminate the surface of a subject will penetrate intothe skin. The extent to which the light penetrates will depend upon thewavelength of the particular radiation. For example, with respect tovisible light, the longer the wavelength, the farther the light willpenetrate into the skin. For example, only about 32% of 400 nm violetlight penetrates into the dermis of human skin, while greater than 85%of 700 nm red light penetrates into the dermis or beyond (see, CapineraJ. L., “Photodynamic Action in Pest Control and Medicine”, Encyclopediaof Entomology, 2nd Edition, Springer Science, 2008, pp. 2850-2862, thecontent of which is hereby incorporated herein by reference in itsentirety for all purposes). For purposes of the present disclosure, whenreferring to “illuminating a tissue,” “reflecting light off of thesurface,” and the like, it is meant that radiation of a suitablewavelength for detection is backscattered from a tissue of a subject,regardless of the distance into the subject the light travels. Forexample, certain wavelengths of infra-red radiation penetrate below thesurface of the skin, thus illuminating the tissue below the surface ofthe subject.

Briefly, light from the illuminator(s) on the systems described hereinpenetrates the subject's superficial tissue and photons scatter in thetissue, bouncing inside the tissue many times. Some photons are absorbedby oxygenated hemoglobin molecules at a known profile across thespectrum of light. Likewise for photons absorbed by de-oxygenatedhemoglobin molecules. The images resolved by the optical detectorsconsist of the photons of light that scatter back through the skin tothe lens subsystem. In this fashion, the images represent the light thatis not absorbed by the various chromophores in the tissue or lost toscattering within the tissue. In some embodiments, light from theilluminators that does not penetrate the surface of the tissue iseliminated by use of polarizers. Likewise, some photons bounce off thesurface of the skin into air, like sunlight reflecting off a lake.

Accordingly, different wavelengths of light may be used to examinedifferent depths of a subject's skin tissue. Generally, high frequency,short-wavelength visible light is useful for investigating elementspresent in the epidermis, while lower frequency, long-wavelength visiblelight is useful for investigating both the epidermis and dermis.Furthermore, certain infra-red wavelengths are useful for investigatingthe epidermis, dermis, and subcutaneous tissues.

In the visible and near-infrared (VNIR) spectral range and at lowintensity irradiance, and when thermal effects are negligible, majorlight-tissue interactions include reflection, refraction, scattering andabsorption. For normal collimated incident radiation, the regularreflection of the skin at the air-tissue interface is typically onlyaround 4%-7% in the 250-3000 nanometer (nm) wavelength range. Forfurther details, see Anderson, R. R. et al., “The Optics of Human Skin”,Journal of Investigative Dermatology, 77, pp. 13-19, 1981, the contentof which is hereby incorporated by reference in its entirety for allpurposes. When neglecting the air-tissue interface reflection andassuming total diffusion of incident light after the stratum corneumlayer, the steady state VNIR skin reflectance can be modeled as thelight that first survives the absorption of the epidermis, then reflectsback toward the epidermis layer due the isotropic scattering in thedermis layer, and then finally emerges out of the skin after goingthrough the epidermis layer again.

Accordingly, the systems and methods described herein can be used todiagnose and characterize a wide variety of medical conditions. In oneembodiment, the concentration of one or more skin or blood component isdetermined in order to evaluate a medical condition in a patient.Non-limiting examples of components useful for medical evaluationinclude: deoxyhemoglobin levels, oxyhemoglobin levels, total hemoglobinlevels, oxygen saturation, oxygen perfusion, hydration levels, totalhematocrit levels, melanin levels, collagen levels, and bilirubinlevels. Likewise, the pattern, gradient, or change over time of a skinor blood component can be used to provide information on the medicalcondition of the patient.

Non-limiting examples of conditions that can be evaluated byhyperspectral/multispectral imaging include: tissue ischemia, ulcerformation, ulcer progression, pressure ulcer formation, pressure ulcerprogression, diabetic foot ulcer formation, diabetic foot ulcerprogression, venous stasis, venous ulcer disease, peripheral arterydisease, atherosclerosis, infection, shock, cardiac decompensation,respiratory insufficiency, hypovolemia, the progression of diabetes,congestive heart failure, sepsis, dehydration, hemorrhage, hemorrhagicshock, hypertension, cancer (e.g., detection, diagnosis, or typing oftumors or skin lesions), retinal abnormalities (e.g., diabeticretinopathy, macular degeneration, or corneal dystrophy), skin wounds,burn wounds, exposure to a chemical or biological agent, and aninflammatory response.

In various embodiments, the systems and methods described herein areused to evaluate tissue oximetery and correspondingly, medicalconditions relating to patient health derived from oxygen measurementsin the superficial vasculature. In certain embodiments, the systems andmethods described herein allow for the measurement of oxygenatedhemoglobin, deoxygenated hemoglobin, oxygen saturation, and oxygenperfusion. Processing of these data provide information to assist aphysician with, for example, diagnosis, prognosis, assignment oftreatment, assignment of surgery, and the execution of surgery forconditions such as critical limb ischemia, diabetic foot ulcers,pressure ulcers, peripheral vascular disease, surgical tissue health,etc.

In various embodiments, the systems and methods described herein areused to evaluate diabetic and pressure ulcers. Development of a diabeticfoot ulcer is commonly a result of a break in the barrier between thedermis of the skin and the subcutaneous fat that cushions the footduring ambulation. This rupture can lead to increased pressure on thedermis, resulting in tissue ischemia and eventual death, and ultimatelymanifesting in the form of an ulcer (Frykberg R. G. et al., “Role ofneuropathy and high foot pressures in diabetic foot ulceration”,Diabetes Care, 21(10), 1998:1714-1719). Measurement of oxyhemoglobin,deoxyhemoglobin, and/or oxygen saturation levels byhyperspectral/multispectral imaging can provide medical informationregarding, for example: a likelihood of ulcer formation at an ROI,diagnosis of an ulcer, identification of boundaries for an ulcer,progression or regression of ulcer formation, a prognosis for healing ofan ulcer, the likelihood of amputation resulting from an ulcer. Furtherinformation on hyperspectral/multispectral methods for the detection andcharacterization of ulcers, e.g., diabetic foot ulcers, are found inU.S. Patent Application Publication No. 2007/0038042, and Nouvong, A. etal., “Evaluation of diabetic foot ulcer healing with hyperspectralimaging of oxyhemoglobin and deoxyhemoglobin”, Diabetes Care. 2009November; 32(11):2056-2061, the contents of which are herebyincorporated herein by reference in their entireties for all purposes.

Other examples of medical conditions include, but are not limited to:tissue viability (e.g., whether tissue is dead or living, and/or whetherit is predicted to remain living); tissue ischemia; malignant cells ortissues (e.g., delineating malignant from benign tumors, dysplasias,precancerous tissue, metastasis); tissue infection and/or inflammation;and/or the presence of pathogens (e.g., bacterial or viral counts).Various embodiments may include differentiating different types oftissue from each other, for example, differentiating bone from flesh,skin, and/or vasculature. Various embodiments may exclude thecharacterization of vasculature.

In various embodiments, the systems and methods provided herein can beused during surgery, for example to determine surgical margins, evaluatethe appropriateness of surgical margins before or after a resection,evaluate or monitor tissue viability in near-real time or real-time, orto assist in image-guided surgery. For more information on the use ofhyperspectral/multispectral imaging during surgery, see, Holzer M. S. etal., “Assessment of renal oxygenation during partial nephrectomy usinghyperspectral imaging”, J Urol. 2011 August; 186(2):400-4; Gibbs-StraussS. L. et al., “Nerve-highlighting fluorescent contrast agents forimage-guided surgery”, Mol Imaging. 2011 April; 10(2):91-101; andPanasyuk S. V. et al., “Medical hyperspectral imaging to facilitateresidual tumor identification during surgery”, Cancer Biol Ther. 2007March; 6(3):439-46, the contents of which are hereby incorporated hereinby reference in their entirety for all purposes.

For more information on the use of hyperspectral/multispectral imagingin medical assessments, see, for example: Chin J. A. et al., J VascSurg. 2011 December; 54(6):1679-88; Khaodhiar L. et al., Diabetes Care2007; 30:903-910; Zuzak K. J. et al., Anal Chem. 2002 May 1;74(9):2021-8; Uhr J. W. et al., Transl Res. 2012 May; 159(5):366-75;Chin M. S. et al., J Biomed Opt. 2012 February; 17(2):026010; Liu Z. etal., Sensors (Basel). 2012; 12(1):162-74; Zuzak K. J. et al., Anal Chem.2011 Oct. 1; 83(19):7424-30; Palmer G. M. et al., J Biomed Opt. 2010November-December; 15(6):066021; Jafari-Saraf and Gordon, Ann Vasc Surg.2010 August; 24(6):741-6; Akbari H. et al., IEEE Trans Biomed Eng. 2010August; 57(8):2011-7; Akbari H. et al., Conf Proc IEEE Eng Med Biol Soc.2009:1461-4; Akbari H. et al., Conf Proc IEEE Eng Med Biol Soc.2008:1238-41; Chang S. K. et al., Clin Cancer Res. 2008 Jul. 1;14(13):4146-53; Siddiqi A. M. et al., Cancer. 2008 Feb. 25;114(1):13-21; Liu Z. et al., Appl Opt. 2007 Dec. 1; 46(34):8328-34; ZhiL. et al., Comput Med Imaging Graph. 2007 December; 31(8):672-8;Khaodhiar L. et al., Diabetes Care. 2007 April; 30(4):903-10; Ferris D.G. et al., J Low Genit Tract Dis. 2001 April; 5(2):65-72; Greenman R. L.et al., Lancet. 2005 Nov. 12; 366(9498):1711-7; Sorg B. S. et al., JBiomed Opt. 2005 July-August; 10(4):44004; Gillies R. et al., andDiabetes Technol Ther. 2003; 5(5):847-55, the contents of which arehereby incorporated herein by reference in their entirety for allpurposes.

Exemplary Embodiments

Provided in this section are nonlimiting exemplary embodiments inaccordance with the present disclosure.

Embodiment 1

An imaging device, comprising a lens disposed along an optical axis andconfigured to receive light that has been emitted from a light sourceand backscattered by an object; a plurality of photo-sensors; aplurality of bandpass filters, each respective bandpass filter coveringa corresponding photo-sensor of the plurality of photo-sensors andconfigured to filter light received by the respective photo-sensor,wherein each respective bandpass filter is configured to allow adifferent corresponding spectral band to pass through the respectivebandpass filter; and a plurality of beam splitters in opticalcommunication with the lens and the plurality of photo-sensors, whereineach respective beam splitter in the plurality of beam splitters isconfigured to split the light received by the lens into at least twooptical paths, a first beam splitter in the plurality of beam splittersis in direct optical communication with the lens and a second beamsplitter in the plurality of beam splitters is in indirect opticalcommunication with the lens through the first beam splitter, and theplurality of beam splitters collectively split the light received by thelens into a plurality of optical paths, wherein each respective opticalpath in the plurality of optical paths is configured to direct light toa corresponding photo-sensor in the plurality of photo-sensors throughthe bandpass filter corresponding to the respective photo-sensor.

Embodiment 2

The imaging device of embodiment 1, further comprising at least onelight source having at least a first operating mode and a secondoperating mode.

Embodiment 3

The imaging device of embodiment 2, wherein, in the first operatingmode, the at least one light source emits light substantially within afirst spectral range and in the second operating mode, the at least onelight source emits light substantially within a second spectral range.

Embodiment 4

The imaging device of embodiment 3, wherein each respective bandpassfilter in the plurality of bandpass filters is configured to allow lightcorresponding to either of two discrete spectral bands to pass throughthe respective bandpass filter.

Embodiment 5

The imaging device of embodiment 4, wherein a first of the two discretespectral bands corresponds to a first spectral band that is representedin the first spectral range and not in the second spectral range; and asecond of the two discrete spectral bands corresponds to a secondspectral band that is represented in the second spectral range and notin the first spectral range.

Embodiment 6

The imaging device of any one of embodiments 3-5, wherein the firstspectral range is substantially non-overlapping with the second spectralrange.

Embodiment 7

The imaging device of any one of embodiments 3-6, wherein the firstspectral range is substantially contiguous with the second spectralrange.

Embodiment 8

The imaging device of embodiment 3, wherein the first spectral rangeconsists of 500 nm to 570 nm wavelength light, and the second spectralranges consists of 570 nm to 640 nm wavelength light.

Embodiment 9

The imaging device of embodiment 1, wherein the at least two opticalpaths from a respective beam splitter in the plurality of beam splittersare substantially coplanar.

Embodiment 10

The imaging device of embodiment 1, further comprising a plurality ofbeam steering elements, each respective beam steering element configuredto direct light in a respective optical path to a respectivephoto-sensor, of the plurality of photo-sensors, corresponding to therespective optical path.

Embodiment 11

The imaging device of embodiment 10, wherein at least one of theplurality of beam steering elements is configured to direct lightperpendicular to the optical axis of the lens.

Embodiment 12

The imaging device of embodiment 10, wherein each one of a first subsetof the plurality of beam steering elements is configured to direct lightin a first direction that is perpendicular to the optical axis, and eachone of a second subset of the plurality of beam steering elements isconfigured to direct light in a second direction that is perpendicularto the optical axis and opposite to the first direction.

Embodiment 13

The imaging device of any of any of embodiments 10-12, wherein a sensingplane of each of the plurality of photo-sensors is substantiallyperpendicular to the optical axis.

Embodiment 14

The imaging device of any one of embodiments 2-8, further comprising apolarizer in optical communication with the at least one light source;and a polarization rotator; wherein the polarizer is configured to:receive light from the at least one light source; project a firstportion of the light from the at least one light source onto the object,wherein the first portion of the light is polarized in a first manner;and project a second portion of the light from the at least one lightsource onto the polarization rotator, wherein the second portion of thelight is polarized in a second manner, other than the first manner; andwherein the polarization rotator is configured to: rotate thepolarization of the second portion of the light from the second mannerto the first manner; and project the second portion of the light,polarized in the first manner, onto the object.

Embodiment 15

The imaging device of embodiment 14, wherein the first manner isp-polarization and the second manner is s-polarization.

Embodiment 16

The imaging device of embodiment 14, wherein the first manner iss-polarization and the second manner is p-polarization.

Embodiment 17

The imaging device of any of embodiments 3-8, further comprising acontroller configured to capture a plurality of images from theplurality of photo-sensors by performing a method including: using theat least one light source to illuminate the object with light fallingwithin the first spectral range; capturing a first set of images withthe plurality of photo-sensors, wherein the first set of imagesincludes, for each respective photo-sensor, an image corresponding to afirst spectral band transmitted by the respective bandpass filter,wherein the light falling within the first spectral range includes lightfalling within the first spectral band of each bandpass filter; usingthe at least one light source to illuminate the object with lightfalling within the second spectral range; and capturing a second set ofimages with the plurality of photo-sensors, wherein the second set ofimages includes, for each respective photo-sensor, an imagecorresponding to a second spectral band transmitted by the respectivebandpass filter, wherein the light falling within the second spectralrange includes light falling within the second spectral band of eachbandpass filter.

Embodiment 18

The imaging device of any of embodiments 1-17, wherein the lens has afixed focus distance, the imaging device further comprising: a firstprojector configured to project a first portion of a shape onto theobject; and a second projector configured to project a second portion ofthe shape onto the object; wherein the first portion of the shape andthe second portion of the shape are configured to converge to form theshape when the lens is positioned at a predetermined distance from theobject, the predetermined distance corresponding to the focus distanceof the lens.

Embodiment 19

The imaging device of embodiment 18, wherein the shape indicates aportion of the object that will be imaged by the plurality ofphoto-sensors when an image is captured with the imaging device.

Embodiment 20

The imaging device of embodiment 19, wherein the shape is selected fromthe group consisting of: a rectangle; a square; a circle; and an oval.

Embodiment 21

The imaging device of any of embodiments 18-20, wherein the firstportion of the shape is a first pair of lines forming a right angle, andthe second portion of the shape is a second pair of lines forming aright angle, wherein, the first portion of the shape and the secondportion of the shape are configured to form a rectangle on the objectwhen the imaging device is positioned at a predetermined distance fromthe object.

Embodiment 22

The imaging device of any of embodiments 1-21, wherein each of theplurality of beam splitters exhibits a ratio of light transmission tolight reflection of about 50:50.

Embodiment 23

The imaging device of embodiment 22, wherein at least one of the beamsplitters in the plurality of beam splitters is a dichroic beamsplitter.

Embodiment 24

The imaging device of embodiment 23, wherein at least the first beamsplitter is a dichroic beam splitter.

Embodiment 25

The imaging device of embodiment 1, further comprising: at least onelight source having at least a first operating mode and a secondoperating mode, and wherein each of the plurality of beam splittersexhibits a ratio of light transmission to light reflection of about50:50, at least one of the beam splitters in the plurality of beamsplitters is a dichroic beam splitter, in the first operating mode, theat least one light source emits light substantially within a firstspectral range that includes at least two discontinuous spectralsub-ranges; and in the second operating mode, the at least one lightsource emits light substantially within a second spectral range.

Embodiment 26

The imaging device of embodiment 25, wherein the first beam splitter isconfigured to transmit light falling within a third spectral range andreflect light falling within a fourth spectral range.

Embodiment 27

The imaging device of embodiment 26, wherein the plurality of beamsplitters includes the first beam splitter, the second beam splitter,and a third beam splitter.

Embodiment 28

The imaging device of embodiment 27, wherein the light falling withinthe third spectral range is transmitted toward the second beam splitter,and the light falling within the fourth spectral range is reflectedtoward the third beam splitter.

Embodiment 29

The imaging device of embodiment 28, wherein the second and the thirdbeam splitters are wavelength-independent beam splitters.

Embodiment 30

The imaging device of any of embodiments 25-29, wherein the at least twodiscontinuous spectral sub-ranges of the first spectral range include: afirst spectral sub-range of about 450-550 nm; and a second spectralsub-range of about 615-650 nm; and the second spectral range is about550-615 nm.

Embodiment 31

The imaging device of any of embodiments 26-30, wherein the thirdspectral range is about 585-650 nm; and the fourth spectral range isabout 450-585 nm.

Embodiment 32

The imaging device of any one of embodiments 26-31, wherein the thirdspectral range includes light falling within both the first and thesecond spectral ranges; and the fourth spectral range includes lightfalling within both the first and the second spectral ranges.

Embodiment 33

The imaging device of any one of embodiments 24-32, wherein the firstbeam splitter is a plate dichroic beam splitter or a block dichroic beamsplitter.

Embodiment 34

The imaging device of embodiment 23, wherein the first beam splitter,the second beam splitter, and the third beam splitter are dichroic beamsplitters.

Embodiment 35

The imaging device of embodiment 34, wherein: in the first operatingmode, the at least one light source emits light substantially within afirst spectral range that includes at least two discontinuous spectralsub-ranges; and in the second operating mode, the at least one lightsource emits light substantially within a second spectral range.

Embodiment 36

The imaging device of embodiment 35, wherein the first beam splitter isconfigured to transmit light falling within a third spectral range thatincludes at least two discontinuous spectral sub-ranges and reflectlight falling within a fourth spectral range that includes at least twodiscontinuous spectral sub-ranges.

Embodiment 37

The imaging device of embodiment 36, wherein the plurality of beamsplitters includes the first beam splitter, the second beam splitter,and a third beam splitter.

Embodiment 38

The imaging device of embodiment 37, wherein the light falling withinthe third spectral range is transmitted toward the second beam splitter,and the light falling within the fourth spectral range is reflectedtoward the third beam splitter.

Embodiment 39

The imaging device of embodiment 38, wherein the second beam splitter isconfigured to reflect light falling within a fifth spectral range thatincludes at least two discontinuous spectral sub-ranges and transmitlight not falling within either of the at least two discontinuousspectral sub-ranges of the fifth spectral sub-range.

Embodiment 40

The imaging device of embodiment 38 or embodiment 39, wherein the thirdbeam splitter is configured to reflect light falling within a sixthspectral range that includes at least two discontinuous spectralsub-ranges and transmit light not falling within either of the at leasttwo discontinuous spectral sub-ranges of the sixth spectral sub-range.

Embodiment 41

The imaging device of any of embodiments 35-40, wherein: the at leasttwo discontinuous spectral sub-ranges of the first spectral rangeinclude: a first spectral sub-range of about 450-530 nm; and a secondspectral sub-range of about 600-650 nm; and the second spectral range isabout 530-600 nm.

Embodiment 42

The imaging device of any of embodiments 36-41, wherein: the at leasttwo discontinuous spectral sub-ranges of the third spectral rangeinclude: a third spectral sub-range of about 570-600 nm; and a fourthspectral sub-range of about 615-650 nm; and the at least twodiscontinuous spectral sub-ranges of the fourth spectral range include:a fifth spectral sub-range of about 450-570 nm; and a sixth spectralsub-range of about 600-615 nm.

Embodiment 43

The imaging device of any of embodiments 39-42, wherein: the at leasttwo discontinuous spectral sub-ranges of the fifth spectral rangeinclude: a seventh spectral sub-range of about 585-595 nm; and an eighthspectral sub-range of about 615-625 nm.

Embodiment 44

The imaging device of any of embodiments 40-43, wherein: the at leasttwo discontinuous spectral sub-ranges of the sixth spectral rangeinclude: a ninth spectral sub-range of about 515-525 nm; and a tenthspectral sub-range of about 555-565 nm.

Embodiment 45

The imaging device of any of embodiments 34-44, wherein the first beamsplitter, the second beam splitter, and the third beam splitter are eacheither a plate dichroic beam splitter or a block dichroic beam splitter.

Embodiment 46

The imaging device of any of embodiments 3-7, wherein the at least onelight source includes a first set of light emitting diodes (LEDs) and asecond set of LEDs; each LED of the first set of LEDs transmits lightthrough a first bandpass filter of the plurality of bandpass filtersthat is configured to block light falling outside the first spectralrange and transmit light falling within the first spectral range; andeach LED of the second set of LEDs transmits light through a secondbandpass filter of the plurality of bandpass filters that is configuredto block light falling outside the second spectral range and transmitlight falling within the second spectral range.

Embodiment 47

The imaging device of embodiment 46, wherein the first set of LEDs arein a first lighting assembly and the second LEDs are in a secondlighting assembly separate from the first lighting assembly.

Embodiment 48

The imaging device of embodiment 46, wherein the first set of LEDs andthe second set of LEDs are in a common lighting assembly.

Embodiment 49

An optical assembly for an imaging device, comprising: a lens disposedalong an optical axis; an optical path assembly configured to receivelight from the lens; a first circuit board positioned on a first side ofthe optical path assembly; and a second circuit board positioned on asecond side of the optical path assembly opposite to the first side,wherein the second circuit board is substantially parallel with thefirst circuit board; wherein the optical path assembly includes: a firstbeam splitter configured to split light received from the lens into afirst optical path and a second optical path, wherein the first opticalpath is substantially collinear with the optical axis, and the secondoptical path is substantially perpendicular to the optical axis; asecond beam splitter configured split light from the first optical pathinto a third optical path and a fourth optical path, wherein the thirdoptical path is substantially collinear with the first optical path, andthe fourth optical path is substantially perpendicular to the opticalaxis; a third beam splitter configured to split light from the secondoptical path into a fifth optical path and a sixth optical path, whereinthe fifth optical path is substantially collinear with the secondoptical path, and the sixth optical path is substantially perpendicularto the second optical path; a first beam steering element configured todeflect light from the third optical path perpendicular to the thirdoptical path and onto a first photo-sensor coupled to the first circuitboard; a second beam steering element configured to deflect light fromthe fourth optical path perpendicular to the fourth optical path andonto a second photo-sensor coupled to the second circuit board; a thirdbeam steering element configured to deflect light from the fifth opticalpath perpendicular to the fifth optical path and onto a thirdphoto-sensor coupled to the first circuit board; and a fourth beamsteering element configured to deflect light from the sixth optical pathperpendicular to the sixth optical path and onto a fourth photo-sensorcoupled to the second circuit board.

Embodiment 50

The optical assembly of embodiment 49, further comprising a plurality ofbandpass filters, the plurality of bandpass filters comprising: a firstbandpass filter positioned in the third optical path between the firstbeam splitter and the first photo-sensor; a second bandpass filterpositioned in the fourth optical path between the second beam splitterand the second photo-sensor; a third bandpass filter positioned in thefifth optical path between the third beam splitter and the thirdphoto-sensor; and a fourth bandpass filter positioned in the sixthoptical path between the fourth beam splitter and the fourthphoto-sensor, wherein each respective bandpass filter in the pluralityof bandpass filters is configured to allow a different respectivespectral band to pass through the respective bandpass filter.

Embodiment 51

The optical assembly of embodiment 50, wherein at least one respectivebandpass filter in the plurality of bandpass filters is a dual bandpassfilter.

Embodiment 52

The optical assembly of any one of embodiments 49-51, further comprisinga polarizing filter disposed along the optical axis.

Embodiment 53

The optical assembly of embodiment 52, wherein the polarizing filter isadjacent to the lens and before the first beam splitter along theoptical axis.

Embodiment 54

The optical assembly of any one of embodiments 49-53, wherein the firstbeam steering element is a mirror or prism.

Embodiment 55

The optical assembly of any of embodiments 49-53, wherein the first beamsteering element is a folding prism.

Embodiment 56

The optical assembly of any one of embodiments 49-55, wherein eachrespective beam splitter and each respective beam steering element isoriented along substantially the same plane.

Embodiment 57

The optical assembly of any of embodiments 49-56, wherein eachrespective photo-sensor is flexibly coupled to its corresponding circuitboard.

Embodiment 58

The optical assembly of any one of embodiments 49-57, wherein the firstbeam splitter, the second beam splitter, and the third beam splittereach exhibits a ratio of light transmission to light reflection of about50:50.

Embodiment 59

The optical assembly of any one of embodiments 49-57, wherein at leastthe first beam splitter is a dichroic beam splitter.

Embodiment 60

The optical assembly of embodiment 59, wherein the first beam splitteris configured to transmit light falling within a first spectral rangeand reflect light falling within a second spectral range.

Embodiment 61

The optical assembly of embodiment 60, wherein the light falling withinthe first spectral range is transmitted toward the second beam splitter,and the light falling within the second spectral range is reflectedtoward the third beam splitter.

Embodiment 62

The optical assembly of embodiment 61, wherein the second and the thirdbeam splitters are wavelength-independent beam splitters.

Embodiment 63

The optical assembly of any one of embodiments 49-57, wherein the firstbeam splitter, the second beam splitter, and the third beam splitter aredichroic beam splitters.

Embodiment 64

The optical assembly of embodiment 63, wherein the first beam splitteris configured to transmit light falling within a first spectral rangethat includes at least two discontinuous spectral sub-ranges and reflectlight falling within a second spectral range that includes at least twodiscontinuous spectral sub-ranges.

Embodiment 65

The optical assembly of any one of embodiments 63-64, wherein the secondbeam splitter is configured to reflect light falling within a thirdspectral range that includes at least two discontinuous spectralsub-ranges and transmit light not falling within either of the at leasttwo discontinuous spectral sub-ranges of the third spectral sub-range.

Embodiment 66

The optical assembly of any one of embodiments 63-65, wherein the thirdbeam splitter is configured to reflect light falling within a fourthspectral range that includes at least two discontinuous spectralsub-ranges and transmit light not falling within either of the at leasttwo discontinuous spectral sub-ranges of the fourth spectral sub-range.

Embodiment 67

A lighting assembly for an imaging device, comprising: at least onelight source; a polarizer in optical communication with the at least onelight source; and a polarization rotator; wherein the polarizer isconfigured to: receive light from the at least one light source; projecta first portion of the light from the at least one light source onto anobject, wherein the first portion of the light exhibits a first type ofpolarization; and project a second portion of the light from the atleast one light source onto the polarization rotator, wherein the secondportion of the light exhibits a second type of polarization; and whereinthe polarization rotator is configured to: rotate the polarization ofthe second portion of the light from the second type of polarization tothe first type of polarization; and project the light of the first typeof polarization onto the object.

Embodiment 68

The lighting assembly of embodiment 67, wherein the first type ofpolarization is p-polarization and the second type of polarization iss-polarization.

Embodiment 69

The lighting assembly of embodiment 67, wherein the first type ofpolarization is s-polarization and the second type of polarization isp-polarization.

Embodiment 70

The lighting assembly of any of embodiments 67-69, wherein the at leastone light source is one or more light emitting diode (LED).

Embodiment 71

The lighting assembly of any of embodiments 67-70, wherein the at leastone light source has two or more operating modes, each respectiveoperating mode in the two or more operation modes includes emission of adiscrete spectral range of light, wherein none of the respectivespectral ranges of light corresponding to an operating mode completelyoverlaps with any other respective spectral range of light correspondingto a different operating mode.

Embodiment 72

The lighting assembly of any of embodiments 67-71, wherein at least 95%of all of the light received by the polarizer from the at least onelight source is illuminated onto the object.

Embodiment 73

A method for capturing a hyper-spectral/multispectral image of anobject, comprising: at an imaging system comprising: at least one lightsource; a lens configured to receive light that has been emitted fromthe at least one light source and backscattered by an object; aplurality of photo-sensors; and a plurality of bandpass filters, eachrespective bandpass filter in the plurality of bandpass filters coveringa respective photo-sensor of the plurality of photo sensors andconfigured to filter light received by the respective photo-sensor,wherein each respective bandpass filter is configured to allow adifferent respective spectral band to pass through the respectivebandpass filter; illuminating the object with the at least one lightsource according to a first mode of operation of the at least one lightsource; capturing a first plurality of images, each of the firstplurality of images being captured by a respective one of the pluralityof photo-sensors, wherein each respective image of the first pluralityof images includes light having a different respective spectral band.

Embodiment 74

The method of embodiment 73, wherein each of the plurality of bandpassfilters is configured to allow light corresponding to either of twodiscrete spectral bands to pass through the filter, the method furthercomprising: after capturing the first plurality of images: illuminatingthe object with the at least one light source according to a second modeof operation of the at least one light source; capturing a secondplurality of images, each of the second plurality of images beingcaptured by a respective one of the plurality of photo-sensors, wherein:each respective image of the second plurality of images includes lighthaving a different respective spectral band; and the spectral bandscaptured by the second plurality of images are different than thespectral bands captured by the first plurality of images.

Embodiment 75

The method of any of embodiments 73-74, wherein the at least one lightsource comprises a plurality of light emitting diodes (LEDs).

Embodiment 76

The method of embodiment 75, wherein a first wavelength optical filteris disposed along an illumination optical path between a first subset ofLEDs in the plurality of LEDs and the object; and a second wavelengthoptical filter is disposed along an illumination optical path between asecond subset of LEDs in the plurality of LEDs and the object, whereinthe first wavelength optical filter and the second wavelength opticalfilter are configured to allow light corresponding to different spectralbands to pass through the respective filters.

Embodiment 77

The method of embodiment 76, wherein the plurality of LEDs comprisewhite light-emitting LEDs.

Embodiment 78

The method of embodiment 75, wherein the plurality of LEDs comprises afirst subset of LEDs configured to emit light corresponding to a firstspectral band of light and a second subset of LEDs configured to emitlight corresponding to a second spectral band of light: illuminating theobject with the at least one light source according to a first mode ofoperation consisting of illuminating the object with light emitted fromthe first subset of LEDs; and illuminating the object with the at leastone light source according to a second mode of operation consisting ofilluminating the object with light emitted from the second subset ofLEDs, wherein the wavelengths of the first spectral band of light andthe wavelengths of the second spectral band of light do not completelyoverlap.

Embodiment 79

An imaging device, comprising: at least one light source having at leasttwo operating modes; a lens disposed along an optical axis andconfigured to receive light that has been emitted from the at least onelight source and backscattered by an object; a plurality ofphoto-sensors; a plurality of bandpass filters, each respective bandpassfilter covering a corresponding photo-sensor of the plurality ofphoto-sensors and configured to filter light received by thecorresponding photo-sensor, wherein each respective bandpass filter isconfigured to allow a different respective spectral band to pass throughthe respective bandpass filter; and one or more beam splitters inoptical communication with the lens and the plurality of photo-sensors,wherein each respective beam splitter is configured to split the lightreceived by the lens into a plurality of optical paths, each opticalpath configured to direct light to a corresponding photo-sensor of theplurality of photo-sensors through the bandpass filter corresponding tothe corresponding photo-sensor.

It will also be understood that, although the terms “first,” “second,”etc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another. For example, a first contact couldbe termed a second contact, and, similarly, a second contact could betermed a first contact, which changing the meaning of the description,so long as all occurrences of the “first contact” are renamedconsistently and all occurrences of the second contact are renamedconsistently. The first contact and the second contact are bothcontacts, but they are not the same contact.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the claims. Asused in the description of the embodiments and the appended claims, thesingular forms “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willalso be understood that the term “and/or” as used herein refers to andencompasses any and all possible combinations of one or more of theassociated listed items. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

As used herein, the term “if” may be construed to mean “when” or “upon”or “in response to determining” or “in accordance with a determination”or “in response to detecting,” that a stated condition precedent istrue, depending on the context. Similarly, the phrase “if it isdetermined [that a stated condition precedent is true]” or “if [a statedcondition precedent is true]” or “when [a stated condition precedent istrue]” may be construed to mean “upon determining” or “in response todetermining” or “in accordance with a determination” or “upon detecting”or “in response to detecting” that the stated condition precedent istrue, depending on the context.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. An imaging device, comprising: a lens disposedalong an optical axis and configured to receive light; a plurality ofphoto-sensors; an optical path assembly comprising a plurality of beamsplitters in optical communication with the lens and the plurality ofphoto-sensors; and a plurality of multi-bandpass filters, wherein eachrespective multi-bandpass filter in the plurality of multi-bandpassfilters covers a corresponding photo-sensor in the plurality ofphoto-sensors thereby selectively allowing a different correspondingspectral band of light, from the light received by the lens and split bythe plurality of beam splitters, to pass through to the correspondingphoto-sensor; wherein each respective beam splitter in the plurality ofbeam splitters is configured to split the light received by the lensinto at least two optical paths, a first beam splitter in the pluralityof beam splitters is in direct optical communication with the lens and asecond beam splitter in the plurality of beam splitters is in indirectoptical communication with the lens through the first beam splitter, andthe plurality of beam splitters collectively split light received by thelens into a plurality of optical paths, wherein each respective opticalpath in the plurality of optical paths is configured to direct light toa corresponding photo-sensor in the plurality of photo-sensors throughthe respective multi-bandpass filter covering the correspondingphoto-sensor.
 2. The imaging device of claim 1, wherein the plurality ofmulti-bandpass filters are dual bandpass filters.
 3. The imaging deviceof claim 1, further comprising a first light source and a second lightsource, wherein the first light source and the second light source areconfigured to shine light so that a portion of the light isbackscattered by the object and received by the lens.
 4. The imagingdevice of claim 3, wherein the first light source emits light that issubstantially limited to a first spectral range, and the second lightsource emits light that is substantially limited to a second spectralrange.
 5. The imaging device of claim 4, wherein the first light sourceis a first multi-spectral light source covered by a first bandpassfilter, wherein the first bandpass filter substantially blocks all lightemitted by the first light source other than the first spectral range,and the second light source is a second multi-spectral light sourcecovered by a second bandpass filter, wherein the second bandpass filtersubstantially blocks all light emitted by the second light source otherthan the second spectral range.
 6. The imaging device of claim 5,wherein the first multi-spectral light source is a first white lightemitting diode and the second multi-spectral light source is a secondwhite light emitting diode.
 7. The imaging device of claim 4, whereineach respective multi-bandpass filter in the plurality of multi-bandpassfilters is configured to selectively allow light corresponding to eitherof two discrete spectral bands to pass through to the correspondingphoto-sensor.
 8. The imaging device of claim 7, wherein: a first of thetwo discrete spectral bands corresponds to a first spectral band that isrepresented in the first spectral range and not in the second spectralrange; and a second of the two discrete spectral bands corresponds to asecond spectral band that is represented in the second spectral rangeand not in the first spectral range.
 9. The imaging device of claim 4,wherein the first spectral range is substantially non-overlapping withthe second spectral range.
 10. The imaging device of claim 4, whereinthe first spectral range is substantially contiguous with the secondspectral range.
 11. The imaging device of claim 4, wherein the firstspectral range comprises 520 nm, 540 nm, 560 nm and 640 nm wavelengthlight and does not include 580 nm, 590 nm, 610 nm and 620 nm wavelengthlight, and the second spectral range comprises 580 nm, 590 nm, 610 nmand 620 nm wavelength light and does not include 520 nm, 540 nm, 560 nmand 640 nm wavelength light.
 12. The imaging device of claim 1, furthercomprising a plurality of beam steering elements, each respective beamsteering element configured to direct light in a respective optical pathto a respective photo-sensor, of the plurality of photo-sensors,corresponding to the respective optical path.
 13. The imaging device ofclaim 12, wherein each one of a first subset of the plurality of beamsteering elements is configured to direct light in a first directionthat is perpendicular to the optical axis, and each one of a secondsubset of the plurality of beam steering elements is configured todirect light in a second direction that is perpendicular to the opticalaxis and opposite to the first direction.
 14. The imaging device ofclaim 4, further comprising a controller configured to capture aplurality of images from the plurality of photo-sensors by performing amethod including: (A) illuminating the object a first time using thefirst light source; (B) capturing a first set of images with theplurality of photo-sensors during the illuminating (A), wherein thefirst set of images includes, for each respective photo-sensor in theplurality of photo-sensors, an image corresponding to a first spectralband transmitted by the corresponding multi-bandpass filter, wherein thelight falling within the first spectral range includes light fallingwithin the first spectral band of each multi-bandpass filter in theplurality of multi-bandpass filters; (C) extinguishing the first lightsource; (D) illuminating the object a second time using the second lightsource; and (E) capturing a second set of images with the plurality ofphoto-sensors during the illuminating (D), wherein the second set ofimages includes, for each respective photo-sensor in the plurality ofphoto-sensors, an image corresponding to a second spectral bandtransmitted by the corresponding multi-bandpass filter, wherein thelight falling within the second spectral range includes light fallingwithin the second spectral band of each multi-bandpass filter in theplurality of multi-bandpass filters.
 15. The imaging device of claim 14,wherein each respective photo-sensor in the plurality of photo-sensorsis a pixel array that is controlled by a corresponding shutter mechanismthat determines an image integration time for the respectivephoto-sensor, and a first photo-sensor in the plurality of photo-sensorsis independently associated with a first integration time for use duringthe capturing (B) and a second integration time for use during thecapturing (E), wherein the first integration time is independent of thesecond integration time.
 16. The imaging device of claim 14, whereineach respective photo-sensor in the plurality of photo-sensors is apixel array that is controlled by a corresponding shutter mechanism thatdetermines an image integration time for the respective photo-sensor, aduration of the illuminating (A) is determined by a first maximumintegration time associated with the plurality of photo-sensors duringthe capturing (B), wherein an integration time of a first photo-sensorin the plurality of photo-sensors is different than an integration timeof a second photo-sensor in the plurality of photo-sensors during thecapturing (B), a duration of the illuminating (D) is determined by asecond maximum integration time associated with the plurality ofphoto-sensors during the capturing (E), wherein an integration time ofthe first photo-sensor is different than an integration time of thesecond photo-sensor during the capturing (E), and the first maximumintegration time is different than the second maximum integration time.17. The imaging device of claim 1, wherein each beam splitter in theplurality of beam splitters exhibits a ratio of light transmission tolight reflection of about 50:50.
 18. The imaging device of claim 17,wherein the beam splitters are wavelength-independent beam splitters.19. The imaging device of claim 3, wherein the first light source is ina first lighting assembly and the second light source is in a secondlighting assembly separate from the first lighting assembly.
 20. Theimaging device of claim 14, wherein each image in the plurality ofimages is a multi-pixel image of a location on the object, the methodfurther comprising: (F) combining each image in the plurality of images,on a pixel by pixel basis, to form a composite image.
 21. The imagingdevice of claim 14, wherein, the imaging device is portable and poweredindependent of a power grid during the illuminating (A) and theilluminating (D), the first light source provides at least 80 watts ofilluminating power during the illuminating (A), the second light sourceprovides at least 80 watts of illuminating power during the illuminating(D), and the imaging device further comprises a capacitor bank inelectrical communication with the first light source and the secondlight source, wherein a capacitor in the capacitor bank has a voltagerating of at least 2 volts and a capacitance rating of at least 80farads.
 22. The imaging device of claim 7, wherein the two discretebands of a multi-bandpass filter in the plurality of multi-bandpassfilters are separated by at least 60 nm.
 23. The imaging device of claim14, wherein the imaging device is portable and electrically independentof a power grid during the illuminating (A) and the illuminating (D),and wherein the illuminating (A) occurs for less than 300 millisecondsand the illuminating (D) occurs for less than 300 milliseconds.
 24. Theimaging device of claim 1, further comprising: a first circuit boardpositioned on a first side of the optical path assembly, wherein a firstphoto-sensor and a third photo-sensor in the plurality of photo-sensorsare coupled to the first circuit board; and a second circuit boardpositioned on a second side of the optical path assembly opposite to thefirst side, wherein the second circuit board is substantially parallelwith the first circuit board, wherein a second photo-sensor and a fourthphoto-sensor in the plurality of photo-sensors are coupled to the secondcircuit board, and wherein: the first beam splitter is configured tosplit light received from the lens into a first optical path and asecond optical path, wherein the first optical path is substantiallycollinear with the optical axis, and the second optical path issubstantially perpendicular to the optical axis, the second beamsplitter is configured split light from the first optical path into athird optical path and a fourth optical path, wherein the third opticalpath is substantially collinear with the first optical path, and thefourth optical path is substantially perpendicular to the optical axis,a third beam splitter in the plurality of beam splitters is configuredto split light from the second optical path into a fifth optical pathand a sixth optical path, wherein the fifth optical path issubstantially collinear with the second optical path, and the sixthoptical path is substantially perpendicular to the second optical path,and wherein the optical path assembly further comprises: a first beamsteering element configured to deflect light from the third optical pathperpendicular to the third optical path and onto the first photo-sensorcoupled to the first circuit board, a second beam steering elementconfigured to deflect light from the fourth optical path perpendicularto the fourth optical path and onto the second photo-sensor coupled tothe second circuit board, a third beam steering element configured todeflect light from the fifth optical path perpendicular to the fifthoptical path and onto the third photo-sensor coupled to the firstcircuit board, and a fourth beam steering element configured to deflectlight from the sixth optical path perpendicular to the sixth opticalpath and onto the fourth photo-sensor coupled to the second circuitboard.
 25. The imaging device of claim 24, wherein a firstmulti-bandpass filter in the plurality of multi-bandpass filters ispositioned in the third optical path between the first beam splitter andthe first photo-sensor, a second multi-bandpass filter in the pluralityof multi-bandpass filters is positioned in the fourth optical pathbetween the second beam splitter and the second photo-sensor, a thirdmulti-bandpass filter in the plurality of multi-bandpass filters ispositioned in the fifth optical path between the third beam splitter andthe third photo-sensor, and a fourth multi-bandpass filter in theplurality of multi-bandpass filters is positioned in the sixth opticalpath between the fourth beam splitter and the fourth photo-sensor. 26.The imaging device of claim 24, further comprising a polarizing filterdisposed along the optical axis.
 27. The imaging device of claim 26,wherein the polarizing filter is adjacent to the lens and before thefirst beam splitter along the optical axis.
 28. The imaging device ofclaim 24, wherein the first beam steering element is a folding prism.29. The imaging device of claim 24, wherein each respective beamsplitter and each respective beam steering element is oriented alongsubstantially the same plane.
 30. The imaging device of claim 24,wherein the first beam splitter, the second beam splitter, and the thirdbeam splitter each exhibits a ratio of light transmission to lightreflection of about 50:50.